1995 lines
81 KiB
Plaintext
1995 lines
81 KiB
Plaintext
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Linux Ethernet Bonding Driver HOWTO
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Latest update: 21 June 2005
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Initial release : Thomas Davis <tadavis at lbl.gov>
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Corrections, HA extensions : 2000/10/03-15 :
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- Willy Tarreau <willy at meta-x.org>
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- Constantine Gavrilov <const-g at xpert.com>
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- Chad N. Tindel <ctindel at ieee dot org>
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- Janice Girouard <girouard at us dot ibm dot com>
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- Jay Vosburgh <fubar at us dot ibm dot com>
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Reorganized and updated Feb 2005 by Jay Vosburgh
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Introduction
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============
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The Linux bonding driver provides a method for aggregating
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multiple network interfaces into a single logical "bonded" interface.
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The behavior of the bonded interfaces depends upon the mode; generally
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speaking, modes provide either hot standby or load balancing services.
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Additionally, link integrity monitoring may be performed.
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The bonding driver originally came from Donald Becker's
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beowulf patches for kernel 2.0. It has changed quite a bit since, and
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the original tools from extreme-linux and beowulf sites will not work
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with this version of the driver.
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For new versions of the driver, updated userspace tools, and
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who to ask for help, please follow the links at the end of this file.
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Table of Contents
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=================
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1. Bonding Driver Installation
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2. Bonding Driver Options
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3. Configuring Bonding Devices
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3.1 Configuration with sysconfig support
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3.1.1 Using DHCP with sysconfig
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3.1.2 Configuring Multiple Bonds with sysconfig
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3.2 Configuration with initscripts support
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3.2.1 Using DHCP with initscripts
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3.2.2 Configuring Multiple Bonds with initscripts
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3.3 Configuring Bonding Manually
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3.3.1 Configuring Multiple Bonds Manually
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5. Querying Bonding Configuration
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5.1 Bonding Configuration
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5.2 Network Configuration
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6. Switch Configuration
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7. 802.1q VLAN Support
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8. Link Monitoring
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8.1 ARP Monitor Operation
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8.2 Configuring Multiple ARP Targets
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8.3 MII Monitor Operation
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9. Potential Trouble Sources
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9.1 Adventures in Routing
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9.2 Ethernet Device Renaming
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9.3 Painfully Slow Or No Failed Link Detection By Miimon
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10. SNMP agents
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11. Promiscuous mode
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12. Configuring Bonding for High Availability
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12.1 High Availability in a Single Switch Topology
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12.2 High Availability in a Multiple Switch Topology
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12.2.1 HA Bonding Mode Selection for Multiple Switch Topology
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12.2.2 HA Link Monitoring for Multiple Switch Topology
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13. Configuring Bonding for Maximum Throughput
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13.1 Maximum Throughput in a Single Switch Topology
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13.1.1 MT Bonding Mode Selection for Single Switch Topology
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13.1.2 MT Link Monitoring for Single Switch Topology
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13.2 Maximum Throughput in a Multiple Switch Topology
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13.2.1 MT Bonding Mode Selection for Multiple Switch Topology
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13.2.2 MT Link Monitoring for Multiple Switch Topology
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14. Switch Behavior Issues
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14.1 Link Establishment and Failover Delays
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14.2 Duplicated Incoming Packets
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15. Hardware Specific Considerations
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15.1 IBM BladeCenter
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16. Frequently Asked Questions
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17. Resources and Links
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1. Bonding Driver Installation
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==============================
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Most popular distro kernels ship with the bonding driver
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already available as a module and the ifenslave user level control
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program installed and ready for use. If your distro does not, or you
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have need to compile bonding from source (e.g., configuring and
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installing a mainline kernel from kernel.org), you'll need to perform
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the following steps:
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1.1 Configure and build the kernel with bonding
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-----------------------------------------------
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The current version of the bonding driver is available in the
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drivers/net/bonding subdirectory of the most recent kernel source
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(which is available on http://kernel.org). Most users "rolling their
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own" will want to use the most recent kernel from kernel.org.
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Configure kernel with "make menuconfig" (or "make xconfig" or
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"make config"), then select "Bonding driver support" in the "Network
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device support" section. It is recommended that you configure the
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driver as module since it is currently the only way to pass parameters
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to the driver or configure more than one bonding device.
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Build and install the new kernel and modules, then continue
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below to install ifenslave.
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1.2 Install ifenslave Control Utility
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-------------------------------------
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The ifenslave user level control program is included in the
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kernel source tree, in the file Documentation/networking/ifenslave.c.
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It is generally recommended that you use the ifenslave that
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corresponds to the kernel that you are using (either from the same
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source tree or supplied with the distro), however, ifenslave
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executables from older kernels should function (but features newer
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than the ifenslave release are not supported). Running an ifenslave
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that is newer than the kernel is not supported, and may or may not
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work.
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To install ifenslave, do the following:
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# gcc -Wall -O -I/usr/src/linux/include ifenslave.c -o ifenslave
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# cp ifenslave /sbin/ifenslave
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If your kernel source is not in "/usr/src/linux," then replace
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"/usr/src/linux/include" in the above with the location of your kernel
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source include directory.
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You may wish to back up any existing /sbin/ifenslave, or, for
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testing or informal use, tag the ifenslave to the kernel version
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(e.g., name the ifenslave executable /sbin/ifenslave-2.6.10).
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IMPORTANT NOTE:
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If you omit the "-I" or specify an incorrect directory, you
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may end up with an ifenslave that is incompatible with the kernel
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you're trying to build it for. Some distros (e.g., Red Hat from 7.1
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onwards) do not have /usr/include/linux symbolically linked to the
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default kernel source include directory.
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2. Bonding Driver Options
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=========================
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Options for the bonding driver are supplied as parameters to
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the bonding module at load time. They may be given as command line
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arguments to the insmod or modprobe command, but are usually specified
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in either the /etc/modules.conf or /etc/modprobe.conf configuration
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file, or in a distro-specific configuration file (some of which are
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detailed in the next section).
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The available bonding driver parameters are listed below. If a
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parameter is not specified the default value is used. When initially
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configuring a bond, it is recommended "tail -f /var/log/messages" be
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run in a separate window to watch for bonding driver error messages.
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It is critical that either the miimon or arp_interval and
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arp_ip_target parameters be specified, otherwise serious network
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degradation will occur during link failures. Very few devices do not
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support at least miimon, so there is really no reason not to use it.
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Options with textual values will accept either the text name
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or, for backwards compatibility, the option value. E.g.,
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"mode=802.3ad" and "mode=4" set the same mode.
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The parameters are as follows:
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arp_interval
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Specifies the ARP link monitoring frequency in milliseconds.
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If ARP monitoring is used in an etherchannel compatible mode
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(modes 0 and 2), the switch should be configured in a mode
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that evenly distributes packets across all links. If the
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switch is configured to distribute the packets in an XOR
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fashion, all replies from the ARP targets will be received on
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the same link which could cause the other team members to
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fail. ARP monitoring should not be used in conjunction with
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miimon. A value of 0 disables ARP monitoring. The default
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value is 0.
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arp_ip_target
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Specifies the IP addresses to use as ARP monitoring peers when
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arp_interval is > 0. These are the targets of the ARP request
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sent to determine the health of the link to the targets.
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Specify these values in ddd.ddd.ddd.ddd format. Multiple IP
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addresses must be separated by a comma. At least one IP
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address must be given for ARP monitoring to function. The
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maximum number of targets that can be specified is 16. The
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default value is no IP addresses.
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downdelay
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Specifies the time, in milliseconds, to wait before disabling
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a slave after a link failure has been detected. This option
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is only valid for the miimon link monitor. The downdelay
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value should be a multiple of the miimon value; if not, it
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will be rounded down to the nearest multiple. The default
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value is 0.
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lacp_rate
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Option specifying the rate in which we'll ask our link partner
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to transmit LACPDU packets in 802.3ad mode. Possible values
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are:
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slow or 0
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Request partner to transmit LACPDUs every 30 seconds
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fast or 1
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Request partner to transmit LACPDUs every 1 second
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The default is slow.
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max_bonds
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Specifies the number of bonding devices to create for this
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instance of the bonding driver. E.g., if max_bonds is 3, and
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the bonding driver is not already loaded, then bond0, bond1
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and bond2 will be created. The default value is 1.
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miimon
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Specifies the MII link monitoring frequency in milliseconds.
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This determines how often the link state of each slave is
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inspected for link failures. A value of zero disables MII
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link monitoring. A value of 100 is a good starting point.
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The use_carrier option, below, affects how the link state is
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determined. See the High Availability section for additional
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information. The default value is 0.
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mode
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Specifies one of the bonding policies. The default is
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balance-rr (round robin). Possible values are:
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balance-rr or 0
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Round-robin policy: Transmit packets in sequential
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order from the first available slave through the
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last. This mode provides load balancing and fault
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tolerance.
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active-backup or 1
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Active-backup policy: Only one slave in the bond is
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active. A different slave becomes active if, and only
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if, the active slave fails. The bond's MAC address is
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externally visible on only one port (network adapter)
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to avoid confusing the switch.
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In bonding version 2.6.2 or later, when a failover
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occurs in active-backup mode, bonding will issue one
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or more gratuitous ARPs on the newly active slave.
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One gratutious ARP is issued for the bonding master
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interface and each VLAN interfaces configured above
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it, provided that the interface has at least one IP
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address configured. Gratuitous ARPs issued for VLAN
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interfaces are tagged with the appropriate VLAN id.
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This mode provides fault tolerance. The primary
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option, documented below, affects the behavior of this
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mode.
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balance-xor or 2
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XOR policy: Transmit based on the selected transmit
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hash policy. The default policy is a simple [(source
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MAC address XOR'd with destination MAC address) modulo
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slave count]. Alternate transmit policies may be
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selected via the xmit_hash_policy option, described
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below.
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This mode provides load balancing and fault tolerance.
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broadcast or 3
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Broadcast policy: transmits everything on all slave
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interfaces. This mode provides fault tolerance.
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802.3ad or 4
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IEEE 802.3ad Dynamic link aggregation. Creates
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aggregation groups that share the same speed and
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duplex settings. Utilizes all slaves in the active
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aggregator according to the 802.3ad specification.
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Slave selection for outgoing traffic is done according
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to the transmit hash policy, which may be changed from
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the default simple XOR policy via the xmit_hash_policy
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option, documented below. Note that not all transmit
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policies may be 802.3ad compliant, particularly in
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regards to the packet mis-ordering requirements of
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section 43.2.4 of the 802.3ad standard. Differing
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peer implementations will have varying tolerances for
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noncompliance.
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Prerequisites:
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1. Ethtool support in the base drivers for retrieving
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the speed and duplex of each slave.
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2. A switch that supports IEEE 802.3ad Dynamic link
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aggregation.
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Most switches will require some type of configuration
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to enable 802.3ad mode.
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balance-tlb or 5
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Adaptive transmit load balancing: channel bonding that
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does not require any special switch support. The
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outgoing traffic is distributed according to the
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current load (computed relative to the speed) on each
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slave. Incoming traffic is received by the current
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slave. If the receiving slave fails, another slave
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takes over the MAC address of the failed receiving
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slave.
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Prerequisite:
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Ethtool support in the base drivers for retrieving the
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speed of each slave.
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balance-alb or 6
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Adaptive load balancing: includes balance-tlb plus
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receive load balancing (rlb) for IPV4 traffic, and
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does not require any special switch support. The
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receive load balancing is achieved by ARP negotiation.
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The bonding driver intercepts the ARP Replies sent by
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the local system on their way out and overwrites the
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source hardware address with the unique hardware
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address of one of the slaves in the bond such that
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different peers use different hardware addresses for
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the server.
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Receive traffic from connections created by the server
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is also balanced. When the local system sends an ARP
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Request the bonding driver copies and saves the peer's
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IP information from the ARP packet. When the ARP
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Reply arrives from the peer, its hardware address is
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retrieved and the bonding driver initiates an ARP
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reply to this peer assigning it to one of the slaves
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in the bond. A problematic outcome of using ARP
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negotiation for balancing is that each time that an
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ARP request is broadcast it uses the hardware address
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of the bond. Hence, peers learn the hardware address
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of the bond and the balancing of receive traffic
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collapses to the current slave. This is handled by
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sending updates (ARP Replies) to all the peers with
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their individually assigned hardware address such that
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the traffic is redistributed. Receive traffic is also
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redistributed when a new slave is added to the bond
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and when an inactive slave is re-activated. The
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receive load is distributed sequentially (round robin)
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among the group of highest speed slaves in the bond.
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When a link is reconnected or a new slave joins the
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bond the receive traffic is redistributed among all
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active slaves in the bond by initiating ARP Replies
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with the selected mac address to each of the
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clients. The updelay parameter (detailed below) must
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be set to a value equal or greater than the switch's
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forwarding delay so that the ARP Replies sent to the
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peers will not be blocked by the switch.
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Prerequisites:
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1. Ethtool support in the base drivers for retrieving
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the speed of each slave.
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2. Base driver support for setting the hardware
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address of a device while it is open. This is
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required so that there will always be one slave in the
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team using the bond hardware address (the
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curr_active_slave) while having a unique hardware
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address for each slave in the bond. If the
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curr_active_slave fails its hardware address is
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swapped with the new curr_active_slave that was
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chosen.
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primary
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A string (eth0, eth2, etc) specifying which slave is the
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primary device. The specified device will always be the
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active slave while it is available. Only when the primary is
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off-line will alternate devices be used. This is useful when
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one slave is preferred over another, e.g., when one slave has
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higher throughput than another.
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The primary option is only valid for active-backup mode.
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updelay
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Specifies the time, in milliseconds, to wait before enabling a
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slave after a link recovery has been detected. This option is
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only valid for the miimon link monitor. The updelay value
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should be a multiple of the miimon value; if not, it will be
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rounded down to the nearest multiple. The default value is 0.
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use_carrier
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Specifies whether or not miimon should use MII or ETHTOOL
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ioctls vs. netif_carrier_ok() to determine the link
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status. The MII or ETHTOOL ioctls are less efficient and
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utilize a deprecated calling sequence within the kernel. The
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netif_carrier_ok() relies on the device driver to maintain its
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state with netif_carrier_on/off; at this writing, most, but
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not all, device drivers support this facility.
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If bonding insists that the link is up when it should not be,
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it may be that your network device driver does not support
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netif_carrier_on/off. The default state for netif_carrier is
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"carrier on," so if a driver does not support netif_carrier,
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it will appear as if the link is always up. In this case,
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setting use_carrier to 0 will cause bonding to revert to the
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MII / ETHTOOL ioctl method to determine the link state.
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A value of 1 enables the use of netif_carrier_ok(), a value of
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0 will use the deprecated MII / ETHTOOL ioctls. The default
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value is 1.
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xmit_hash_policy
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Selects the transmit hash policy to use for slave selection in
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balance-xor and 802.3ad modes. Possible values are:
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layer2
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Uses XOR of hardware MAC addresses to generate the
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hash. The formula is
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(source MAC XOR destination MAC) modulo slave count
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This algorithm will place all traffic to a particular
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network peer on the same slave.
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This algorithm is 802.3ad compliant.
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layer3+4
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This policy uses upper layer protocol information,
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when available, to generate the hash. This allows for
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traffic to a particular network peer to span multiple
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slaves, although a single connection will not span
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multiple slaves.
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The formula for unfragmented TCP and UDP packets is
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((source port XOR dest port) XOR
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((source IP XOR dest IP) AND 0xffff)
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modulo slave count
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For fragmented TCP or UDP packets and all other IP
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protocol traffic, the source and destination port
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information is omitted. For non-IP traffic, the
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formula is the same as for the layer2 transmit hash
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policy.
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This policy is intended to mimic the behavior of
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certain switches, notably Cisco switches with PFC2 as
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well as some Foundry and IBM products.
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This algorithm is not fully 802.3ad compliant. A
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single TCP or UDP conversation containing both
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fragmented and unfragmented packets will see packets
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striped across two interfaces. This may result in out
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of order delivery. Most traffic types will not meet
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this criteria, as TCP rarely fragments traffic, and
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most UDP traffic is not involved in extended
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conversations. Other implementations of 802.3ad may
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or may not tolerate this noncompliance.
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The default value is layer2. This option was added in bonding
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version 2.6.3. In earlier versions of bonding, this parameter does
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not exist, and the layer2 policy is the only policy.
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3. Configuring Bonding Devices
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==============================
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There are, essentially, two methods for configuring bonding:
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with support from the distro's network initialization scripts, and
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without. Distros generally use one of two packages for the network
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initialization scripts: initscripts or sysconfig. Recent versions of
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these packages have support for bonding, while older versions do not.
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We will first describe the options for configuring bonding for
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distros using versions of initscripts and sysconfig with full or
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partial support for bonding, then provide information on enabling
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bonding without support from the network initialization scripts (i.e.,
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older versions of initscripts or sysconfig).
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If you're unsure whether your distro uses sysconfig or
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initscripts, or don't know if it's new enough, have no fear.
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Determining this is fairly straightforward.
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First, issue the command:
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$ rpm -qf /sbin/ifup
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It will respond with a line of text starting with either
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"initscripts" or "sysconfig," followed by some numbers. This is the
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package that provides your network initialization scripts.
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Next, to determine if your installation supports bonding,
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issue the command:
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|
$ grep ifenslave /sbin/ifup
|
|
|
|
If this returns any matches, then your initscripts or
|
|
sysconfig has support for bonding.
|
|
|
|
3.1 Configuration with sysconfig support
|
|
----------------------------------------
|
|
|
|
This section applies to distros using a version of sysconfig
|
|
with bonding support, for example, SuSE Linux Enterprise Server 9.
|
|
|
|
SuSE SLES 9's networking configuration system does support
|
|
bonding, however, at this writing, the YaST system configuration
|
|
frontend does not provide any means to work with bonding devices.
|
|
Bonding devices can be managed by hand, however, as follows.
|
|
|
|
First, if they have not already been configured, configure the
|
|
slave devices. On SLES 9, this is most easily done by running the
|
|
yast2 sysconfig configuration utility. The goal is for to create an
|
|
ifcfg-id file for each slave device. The simplest way to accomplish
|
|
this is to configure the devices for DHCP (this is only to get the
|
|
file ifcfg-id file created; see below for some issues with DHCP). The
|
|
name of the configuration file for each device will be of the form:
|
|
|
|
ifcfg-id-xx:xx:xx:xx:xx:xx
|
|
|
|
Where the "xx" portion will be replaced with the digits from
|
|
the device's permanent MAC address.
|
|
|
|
Once the set of ifcfg-id-xx:xx:xx:xx:xx:xx files has been
|
|
created, it is necessary to edit the configuration files for the slave
|
|
devices (the MAC addresses correspond to those of the slave devices).
|
|
Before editing, the file will contain multiple lines, and will look
|
|
something like this:
|
|
|
|
BOOTPROTO='dhcp'
|
|
STARTMODE='on'
|
|
USERCTL='no'
|
|
UNIQUE='XNzu.WeZGOGF+4wE'
|
|
_nm_name='bus-pci-0001:61:01.0'
|
|
|
|
Change the BOOTPROTO and STARTMODE lines to the following:
|
|
|
|
BOOTPROTO='none'
|
|
STARTMODE='off'
|
|
|
|
Do not alter the UNIQUE or _nm_name lines. Remove any other
|
|
lines (USERCTL, etc).
|
|
|
|
Once the ifcfg-id-xx:xx:xx:xx:xx:xx files have been modified,
|
|
it's time to create the configuration file for the bonding device
|
|
itself. This file is named ifcfg-bondX, where X is the number of the
|
|
bonding device to create, starting at 0. The first such file is
|
|
ifcfg-bond0, the second is ifcfg-bond1, and so on. The sysconfig
|
|
network configuration system will correctly start multiple instances
|
|
of bonding.
|
|
|
|
The contents of the ifcfg-bondX file is as follows:
|
|
|
|
BOOTPROTO="static"
|
|
BROADCAST="10.0.2.255"
|
|
IPADDR="10.0.2.10"
|
|
NETMASK="255.255.0.0"
|
|
NETWORK="10.0.2.0"
|
|
REMOTE_IPADDR=""
|
|
STARTMODE="onboot"
|
|
BONDING_MASTER="yes"
|
|
BONDING_MODULE_OPTS="mode=active-backup miimon=100"
|
|
BONDING_SLAVE0="eth0"
|
|
BONDING_SLAVE1="bus-pci-0000:06:08.1"
|
|
|
|
Replace the sample BROADCAST, IPADDR, NETMASK and NETWORK
|
|
values with the appropriate values for your network.
|
|
|
|
The STARTMODE specifies when the device is brought online.
|
|
The possible values are:
|
|
|
|
onboot: The device is started at boot time. If you're not
|
|
sure, this is probably what you want.
|
|
|
|
manual: The device is started only when ifup is called
|
|
manually. Bonding devices may be configured this
|
|
way if you do not wish them to start automatically
|
|
at boot for some reason.
|
|
|
|
hotplug: The device is started by a hotplug event. This is not
|
|
a valid choice for a bonding device.
|
|
|
|
off or ignore: The device configuration is ignored.
|
|
|
|
The line BONDING_MASTER='yes' indicates that the device is a
|
|
bonding master device. The only useful value is "yes."
|
|
|
|
The contents of BONDING_MODULE_OPTS are supplied to the
|
|
instance of the bonding module for this device. Specify the options
|
|
for the bonding mode, link monitoring, and so on here. Do not include
|
|
the max_bonds bonding parameter; this will confuse the configuration
|
|
system if you have multiple bonding devices.
|
|
|
|
Finally, supply one BONDING_SLAVEn="slave device" for each
|
|
slave. where "n" is an increasing value, one for each slave. The
|
|
"slave device" is either an interface name, e.g., "eth0", or a device
|
|
specifier for the network device. The interface name is easier to
|
|
find, but the ethN names are subject to change at boot time if, e.g.,
|
|
a device early in the sequence has failed. The device specifiers
|
|
(bus-pci-0000:06:08.1 in the example above) specify the physical
|
|
network device, and will not change unless the device's bus location
|
|
changes (for example, it is moved from one PCI slot to another). The
|
|
example above uses one of each type for demonstration purposes; most
|
|
configurations will choose one or the other for all slave devices.
|
|
|
|
When all configuration files have been modified or created,
|
|
networking must be restarted for the configuration changes to take
|
|
effect. This can be accomplished via the following:
|
|
|
|
# /etc/init.d/network restart
|
|
|
|
Note that the network control script (/sbin/ifdown) will
|
|
remove the bonding module as part of the network shutdown processing,
|
|
so it is not necessary to remove the module by hand if, e.g., the
|
|
module parameters have changed.
|
|
|
|
Also, at this writing, YaST/YaST2 will not manage bonding
|
|
devices (they do not show bonding interfaces on its list of network
|
|
devices). It is necessary to edit the configuration file by hand to
|
|
change the bonding configuration.
|
|
|
|
Additional general options and details of the ifcfg file
|
|
format can be found in an example ifcfg template file:
|
|
|
|
/etc/sysconfig/network/ifcfg.template
|
|
|
|
Note that the template does not document the various BONDING_
|
|
settings described above, but does describe many of the other options.
|
|
|
|
3.1.1 Using DHCP with sysconfig
|
|
-------------------------------
|
|
|
|
Under sysconfig, configuring a device with BOOTPROTO='dhcp'
|
|
will cause it to query DHCP for its IP address information. At this
|
|
writing, this does not function for bonding devices; the scripts
|
|
attempt to obtain the device address from DHCP prior to adding any of
|
|
the slave devices. Without active slaves, the DHCP requests are not
|
|
sent to the network.
|
|
|
|
3.1.2 Configuring Multiple Bonds with sysconfig
|
|
-----------------------------------------------
|
|
|
|
The sysconfig network initialization system is capable of
|
|
handling multiple bonding devices. All that is necessary is for each
|
|
bonding instance to have an appropriately configured ifcfg-bondX file
|
|
(as described above). Do not specify the "max_bonds" parameter to any
|
|
instance of bonding, as this will confuse sysconfig. If you require
|
|
multiple bonding devices with identical parameters, create multiple
|
|
ifcfg-bondX files.
|
|
|
|
Because the sysconfig scripts supply the bonding module
|
|
options in the ifcfg-bondX file, it is not necessary to add them to
|
|
the system /etc/modules.conf or /etc/modprobe.conf configuration file.
|
|
|
|
3.2 Configuration with initscripts support
|
|
------------------------------------------
|
|
|
|
This section applies to distros using a version of initscripts
|
|
with bonding support, for example, Red Hat Linux 9 or Red Hat
|
|
Enterprise Linux version 3 or 4. On these systems, the network
|
|
initialization scripts have some knowledge of bonding, and can be
|
|
configured to control bonding devices.
|
|
|
|
These distros will not automatically load the network adapter
|
|
driver unless the ethX device is configured with an IP address.
|
|
Because of this constraint, users must manually configure a
|
|
network-script file for all physical adapters that will be members of
|
|
a bondX link. Network script files are located in the directory:
|
|
|
|
/etc/sysconfig/network-scripts
|
|
|
|
The file name must be prefixed with "ifcfg-eth" and suffixed
|
|
with the adapter's physical adapter number. For example, the script
|
|
for eth0 would be named /etc/sysconfig/network-scripts/ifcfg-eth0.
|
|
Place the following text in the file:
|
|
|
|
DEVICE=eth0
|
|
USERCTL=no
|
|
ONBOOT=yes
|
|
MASTER=bond0
|
|
SLAVE=yes
|
|
BOOTPROTO=none
|
|
|
|
The DEVICE= line will be different for every ethX device and
|
|
must correspond with the name of the file, i.e., ifcfg-eth1 must have
|
|
a device line of DEVICE=eth1. The setting of the MASTER= line will
|
|
also depend on the final bonding interface name chosen for your bond.
|
|
As with other network devices, these typically start at 0, and go up
|
|
one for each device, i.e., the first bonding instance is bond0, the
|
|
second is bond1, and so on.
|
|
|
|
Next, create a bond network script. The file name for this
|
|
script will be /etc/sysconfig/network-scripts/ifcfg-bondX where X is
|
|
the number of the bond. For bond0 the file is named "ifcfg-bond0",
|
|
for bond1 it is named "ifcfg-bond1", and so on. Within that file,
|
|
place the following text:
|
|
|
|
DEVICE=bond0
|
|
IPADDR=192.168.1.1
|
|
NETMASK=255.255.255.0
|
|
NETWORK=192.168.1.0
|
|
BROADCAST=192.168.1.255
|
|
ONBOOT=yes
|
|
BOOTPROTO=none
|
|
USERCTL=no
|
|
|
|
Be sure to change the networking specific lines (IPADDR,
|
|
NETMASK, NETWORK and BROADCAST) to match your network configuration.
|
|
|
|
Finally, it is necessary to edit /etc/modules.conf (or
|
|
/etc/modprobe.conf, depending upon your distro) to load the bonding
|
|
module with your desired options when the bond0 interface is brought
|
|
up. The following lines in /etc/modules.conf (or modprobe.conf) will
|
|
load the bonding module, and select its options:
|
|
|
|
alias bond0 bonding
|
|
options bond0 mode=balance-alb miimon=100
|
|
|
|
Replace the sample parameters with the appropriate set of
|
|
options for your configuration.
|
|
|
|
Finally run "/etc/rc.d/init.d/network restart" as root. This
|
|
will restart the networking subsystem and your bond link should be now
|
|
up and running.
|
|
|
|
3.2.1 Using DHCP with initscripts
|
|
---------------------------------
|
|
|
|
Recent versions of initscripts (the version supplied with
|
|
Fedora Core 3 and Red Hat Enterprise Linux 4 is reported to work) do
|
|
have support for assigning IP information to bonding devices via DHCP.
|
|
|
|
To configure bonding for DHCP, configure it as described
|
|
above, except replace the line "BOOTPROTO=none" with "BOOTPROTO=dhcp"
|
|
and add a line consisting of "TYPE=Bonding". Note that the TYPE value
|
|
is case sensitive.
|
|
|
|
3.2.2 Configuring Multiple Bonds with initscripts
|
|
-------------------------------------------------
|
|
|
|
At this writing, the initscripts package does not directly
|
|
support loading the bonding driver multiple times, so the process for
|
|
doing so is the same as described in the "Configuring Multiple Bonds
|
|
Manually" section, below.
|
|
|
|
NOTE: It has been observed that some Red Hat supplied kernels
|
|
are apparently unable to rename modules at load time (the "-obonding1"
|
|
part). Attempts to pass that option to modprobe will produce an
|
|
"Operation not permitted" error. This has been reported on some
|
|
Fedora Core kernels, and has been seen on RHEL 4 as well. On kernels
|
|
exhibiting this problem, it will be impossible to configure multiple
|
|
bonds with differing parameters.
|
|
|
|
3.3 Configuring Bonding Manually
|
|
--------------------------------
|
|
|
|
This section applies to distros whose network initialization
|
|
scripts (the sysconfig or initscripts package) do not have specific
|
|
knowledge of bonding. One such distro is SuSE Linux Enterprise Server
|
|
version 8.
|
|
|
|
The general method for these systems is to place the bonding
|
|
module parameters into /etc/modules.conf or /etc/modprobe.conf (as
|
|
appropriate for the installed distro), then add modprobe and/or
|
|
ifenslave commands to the system's global init script. The name of
|
|
the global init script differs; for sysconfig, it is
|
|
/etc/init.d/boot.local and for initscripts it is /etc/rc.d/rc.local.
|
|
|
|
For example, if you wanted to make a simple bond of two e100
|
|
devices (presumed to be eth0 and eth1), and have it persist across
|
|
reboots, edit the appropriate file (/etc/init.d/boot.local or
|
|
/etc/rc.d/rc.local), and add the following:
|
|
|
|
modprobe bonding mode=balance-alb miimon=100
|
|
modprobe e100
|
|
ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up
|
|
ifenslave bond0 eth0
|
|
ifenslave bond0 eth1
|
|
|
|
Replace the example bonding module parameters and bond0
|
|
network configuration (IP address, netmask, etc) with the appropriate
|
|
values for your configuration.
|
|
|
|
Unfortunately, this method will not provide support for the
|
|
ifup and ifdown scripts on the bond devices. To reload the bonding
|
|
configuration, it is necessary to run the initialization script, e.g.,
|
|
|
|
# /etc/init.d/boot.local
|
|
|
|
or
|
|
|
|
# /etc/rc.d/rc.local
|
|
|
|
It may be desirable in such a case to create a separate script
|
|
which only initializes the bonding configuration, then call that
|
|
separate script from within boot.local. This allows for bonding to be
|
|
enabled without re-running the entire global init script.
|
|
|
|
To shut down the bonding devices, it is necessary to first
|
|
mark the bonding device itself as being down, then remove the
|
|
appropriate device driver modules. For our example above, you can do
|
|
the following:
|
|
|
|
# ifconfig bond0 down
|
|
# rmmod bonding
|
|
# rmmod e100
|
|
|
|
Again, for convenience, it may be desirable to create a script
|
|
with these commands.
|
|
|
|
|
|
3.3.1 Configuring Multiple Bonds Manually
|
|
-----------------------------------------
|
|
|
|
This section contains information on configuring multiple
|
|
bonding devices with differing options for those systems whose network
|
|
initialization scripts lack support for configuring multiple bonds.
|
|
|
|
If you require multiple bonding devices, but all with the same
|
|
options, you may wish to use the "max_bonds" module parameter,
|
|
documented above.
|
|
|
|
To create multiple bonding devices with differing options, it
|
|
is necessary to load the bonding driver multiple times. Note that
|
|
current versions of the sysconfig network initialization scripts
|
|
handle this automatically; if your distro uses these scripts, no
|
|
special action is needed. See the section Configuring Bonding
|
|
Devices, above, if you're not sure about your network initialization
|
|
scripts.
|
|
|
|
To load multiple instances of the module, it is necessary to
|
|
specify a different name for each instance (the module loading system
|
|
requires that every loaded module, even multiple instances of the same
|
|
module, have a unique name). This is accomplished by supplying
|
|
multiple sets of bonding options in /etc/modprobe.conf, for example:
|
|
|
|
alias bond0 bonding
|
|
options bond0 -o bond0 mode=balance-rr miimon=100
|
|
|
|
alias bond1 bonding
|
|
options bond1 -o bond1 mode=balance-alb miimon=50
|
|
|
|
will load the bonding module two times. The first instance is
|
|
named "bond0" and creates the bond0 device in balance-rr mode with an
|
|
miimon of 100. The second instance is named "bond1" and creates the
|
|
bond1 device in balance-alb mode with an miimon of 50.
|
|
|
|
In some circumstances (typically with older distributions),
|
|
the above does not work, and the second bonding instance never sees
|
|
its options. In that case, the second options line can be substituted
|
|
as follows:
|
|
|
|
install bonding1 /sbin/modprobe bonding -obond1 mode=balance-alb miimon=50
|
|
|
|
This may be repeated any number of times, specifying a new and
|
|
unique name in place of bond1 for each subsequent instance.
|
|
|
|
|
|
5. Querying Bonding Configuration
|
|
=================================
|
|
|
|
5.1 Bonding Configuration
|
|
-------------------------
|
|
|
|
Each bonding device has a read-only file residing in the
|
|
/proc/net/bonding directory. The file contents include information
|
|
about the bonding configuration, options and state of each slave.
|
|
|
|
For example, the contents of /proc/net/bonding/bond0 after the
|
|
driver is loaded with parameters of mode=0 and miimon=1000 is
|
|
generally as follows:
|
|
|
|
Ethernet Channel Bonding Driver: 2.6.1 (October 29, 2004)
|
|
Bonding Mode: load balancing (round-robin)
|
|
Currently Active Slave: eth0
|
|
MII Status: up
|
|
MII Polling Interval (ms): 1000
|
|
Up Delay (ms): 0
|
|
Down Delay (ms): 0
|
|
|
|
Slave Interface: eth1
|
|
MII Status: up
|
|
Link Failure Count: 1
|
|
|
|
Slave Interface: eth0
|
|
MII Status: up
|
|
Link Failure Count: 1
|
|
|
|
The precise format and contents will change depending upon the
|
|
bonding configuration, state, and version of the bonding driver.
|
|
|
|
5.2 Network configuration
|
|
-------------------------
|
|
|
|
The network configuration can be inspected using the ifconfig
|
|
command. Bonding devices will have the MASTER flag set; Bonding slave
|
|
devices will have the SLAVE flag set. The ifconfig output does not
|
|
contain information on which slaves are associated with which masters.
|
|
|
|
In the example below, the bond0 interface is the master
|
|
(MASTER) while eth0 and eth1 are slaves (SLAVE). Notice all slaves of
|
|
bond0 have the same MAC address (HWaddr) as bond0 for all modes except
|
|
TLB and ALB that require a unique MAC address for each slave.
|
|
|
|
# /sbin/ifconfig
|
|
bond0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
|
|
inet addr:XXX.XXX.XXX.YYY Bcast:XXX.XXX.XXX.255 Mask:255.255.252.0
|
|
UP BROADCAST RUNNING MASTER MULTICAST MTU:1500 Metric:1
|
|
RX packets:7224794 errors:0 dropped:0 overruns:0 frame:0
|
|
TX packets:3286647 errors:1 dropped:0 overruns:1 carrier:0
|
|
collisions:0 txqueuelen:0
|
|
|
|
eth0 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
|
|
inet addr:XXX.XXX.XXX.YYY Bcast:XXX.XXX.XXX.255 Mask:255.255.252.0
|
|
UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
|
|
RX packets:3573025 errors:0 dropped:0 overruns:0 frame:0
|
|
TX packets:1643167 errors:1 dropped:0 overruns:1 carrier:0
|
|
collisions:0 txqueuelen:100
|
|
Interrupt:10 Base address:0x1080
|
|
|
|
eth1 Link encap:Ethernet HWaddr 00:C0:F0:1F:37:B4
|
|
inet addr:XXX.XXX.XXX.YYY Bcast:XXX.XXX.XXX.255 Mask:255.255.252.0
|
|
UP BROADCAST RUNNING SLAVE MULTICAST MTU:1500 Metric:1
|
|
RX packets:3651769 errors:0 dropped:0 overruns:0 frame:0
|
|
TX packets:1643480 errors:0 dropped:0 overruns:0 carrier:0
|
|
collisions:0 txqueuelen:100
|
|
Interrupt:9 Base address:0x1400
|
|
|
|
6. Switch Configuration
|
|
=======================
|
|
|
|
For this section, "switch" refers to whatever system the
|
|
bonded devices are directly connected to (i.e., where the other end of
|
|
the cable plugs into). This may be an actual dedicated switch device,
|
|
or it may be another regular system (e.g., another computer running
|
|
Linux),
|
|
|
|
The active-backup, balance-tlb and balance-alb modes do not
|
|
require any specific configuration of the switch.
|
|
|
|
The 802.3ad mode requires that the switch have the appropriate
|
|
ports configured as an 802.3ad aggregation. The precise method used
|
|
to configure this varies from switch to switch, but, for example, a
|
|
Cisco 3550 series switch requires that the appropriate ports first be
|
|
grouped together in a single etherchannel instance, then that
|
|
etherchannel is set to mode "lacp" to enable 802.3ad (instead of
|
|
standard EtherChannel).
|
|
|
|
The balance-rr, balance-xor and broadcast modes generally
|
|
require that the switch have the appropriate ports grouped together.
|
|
The nomenclature for such a group differs between switches, it may be
|
|
called an "etherchannel" (as in the Cisco example, above), a "trunk
|
|
group" or some other similar variation. For these modes, each switch
|
|
will also have its own configuration options for the switch's transmit
|
|
policy to the bond. Typical choices include XOR of either the MAC or
|
|
IP addresses. The transmit policy of the two peers does not need to
|
|
match. For these three modes, the bonding mode really selects a
|
|
transmit policy for an EtherChannel group; all three will interoperate
|
|
with another EtherChannel group.
|
|
|
|
|
|
7. 802.1q VLAN Support
|
|
======================
|
|
|
|
It is possible to configure VLAN devices over a bond interface
|
|
using the 8021q driver. However, only packets coming from the 8021q
|
|
driver and passing through bonding will be tagged by default. Self
|
|
generated packets, for example, bonding's learning packets or ARP
|
|
packets generated by either ALB mode or the ARP monitor mechanism, are
|
|
tagged internally by bonding itself. As a result, bonding must
|
|
"learn" the VLAN IDs configured above it, and use those IDs to tag
|
|
self generated packets.
|
|
|
|
For reasons of simplicity, and to support the use of adapters
|
|
that can do VLAN hardware acceleration offloading, the bonding
|
|
interface declares itself as fully hardware offloading capable, it gets
|
|
the add_vid/kill_vid notifications to gather the necessary
|
|
information, and it propagates those actions to the slaves. In case
|
|
of mixed adapter types, hardware accelerated tagged packets that
|
|
should go through an adapter that is not offloading capable are
|
|
"un-accelerated" by the bonding driver so the VLAN tag sits in the
|
|
regular location.
|
|
|
|
VLAN interfaces *must* be added on top of a bonding interface
|
|
only after enslaving at least one slave. The bonding interface has a
|
|
hardware address of 00:00:00:00:00:00 until the first slave is added.
|
|
If the VLAN interface is created prior to the first enslavement, it
|
|
would pick up the all-zeroes hardware address. Once the first slave
|
|
is attached to the bond, the bond device itself will pick up the
|
|
slave's hardware address, which is then available for the VLAN device.
|
|
|
|
Also, be aware that a similar problem can occur if all slaves
|
|
are released from a bond that still has one or more VLAN interfaces on
|
|
top of it. When a new slave is added, the bonding interface will
|
|
obtain its hardware address from the first slave, which might not
|
|
match the hardware address of the VLAN interfaces (which was
|
|
ultimately copied from an earlier slave).
|
|
|
|
There are two methods to insure that the VLAN device operates
|
|
with the correct hardware address if all slaves are removed from a
|
|
bond interface:
|
|
|
|
1. Remove all VLAN interfaces then recreate them
|
|
|
|
2. Set the bonding interface's hardware address so that it
|
|
matches the hardware address of the VLAN interfaces.
|
|
|
|
Note that changing a VLAN interface's HW address would set the
|
|
underlying device -- i.e. the bonding interface -- to promiscuous
|
|
mode, which might not be what you want.
|
|
|
|
|
|
8. Link Monitoring
|
|
==================
|
|
|
|
The bonding driver at present supports two schemes for
|
|
monitoring a slave device's link state: the ARP monitor and the MII
|
|
monitor.
|
|
|
|
At the present time, due to implementation restrictions in the
|
|
bonding driver itself, it is not possible to enable both ARP and MII
|
|
monitoring simultaneously.
|
|
|
|
8.1 ARP Monitor Operation
|
|
-------------------------
|
|
|
|
The ARP monitor operates as its name suggests: it sends ARP
|
|
queries to one or more designated peer systems on the network, and
|
|
uses the response as an indication that the link is operating. This
|
|
gives some assurance that traffic is actually flowing to and from one
|
|
or more peers on the local network.
|
|
|
|
The ARP monitor relies on the device driver itself to verify
|
|
that traffic is flowing. In particular, the driver must keep up to
|
|
date the last receive time, dev->last_rx, and transmit start time,
|
|
dev->trans_start. If these are not updated by the driver, then the
|
|
ARP monitor will immediately fail any slaves using that driver, and
|
|
those slaves will stay down. If networking monitoring (tcpdump, etc)
|
|
shows the ARP requests and replies on the network, then it may be that
|
|
your device driver is not updating last_rx and trans_start.
|
|
|
|
8.2 Configuring Multiple ARP Targets
|
|
------------------------------------
|
|
|
|
While ARP monitoring can be done with just one target, it can
|
|
be useful in a High Availability setup to have several targets to
|
|
monitor. In the case of just one target, the target itself may go
|
|
down or have a problem making it unresponsive to ARP requests. Having
|
|
an additional target (or several) increases the reliability of the ARP
|
|
monitoring.
|
|
|
|
Multiple ARP targets must be separated by commas as follows:
|
|
|
|
# example options for ARP monitoring with three targets
|
|
alias bond0 bonding
|
|
options bond0 arp_interval=60 arp_ip_target=192.168.0.1,192.168.0.3,192.168.0.9
|
|
|
|
For just a single target the options would resemble:
|
|
|
|
# example options for ARP monitoring with one target
|
|
alias bond0 bonding
|
|
options bond0 arp_interval=60 arp_ip_target=192.168.0.100
|
|
|
|
|
|
8.3 MII Monitor Operation
|
|
-------------------------
|
|
|
|
The MII monitor monitors only the carrier state of the local
|
|
network interface. It accomplishes this in one of three ways: by
|
|
depending upon the device driver to maintain its carrier state, by
|
|
querying the device's MII registers, or by making an ethtool query to
|
|
the device.
|
|
|
|
If the use_carrier module parameter is 1 (the default value),
|
|
then the MII monitor will rely on the driver for carrier state
|
|
information (via the netif_carrier subsystem). As explained in the
|
|
use_carrier parameter information, above, if the MII monitor fails to
|
|
detect carrier loss on the device (e.g., when the cable is physically
|
|
disconnected), it may be that the driver does not support
|
|
netif_carrier.
|
|
|
|
If use_carrier is 0, then the MII monitor will first query the
|
|
device's (via ioctl) MII registers and check the link state. If that
|
|
request fails (not just that it returns carrier down), then the MII
|
|
monitor will make an ethtool ETHOOL_GLINK request to attempt to obtain
|
|
the same information. If both methods fail (i.e., the driver either
|
|
does not support or had some error in processing both the MII register
|
|
and ethtool requests), then the MII monitor will assume the link is
|
|
up.
|
|
|
|
9. Potential Sources of Trouble
|
|
===============================
|
|
|
|
9.1 Adventures in Routing
|
|
-------------------------
|
|
|
|
When bonding is configured, it is important that the slave
|
|
devices not have routes that supercede routes of the master (or,
|
|
generally, not have routes at all). For example, suppose the bonding
|
|
device bond0 has two slaves, eth0 and eth1, and the routing table is
|
|
as follows:
|
|
|
|
Kernel IP routing table
|
|
Destination Gateway Genmask Flags MSS Window irtt Iface
|
|
10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth0
|
|
10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth1
|
|
10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 bond0
|
|
127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo
|
|
|
|
This routing configuration will likely still update the
|
|
receive/transmit times in the driver (needed by the ARP monitor), but
|
|
may bypass the bonding driver (because outgoing traffic to, in this
|
|
case, another host on network 10 would use eth0 or eth1 before bond0).
|
|
|
|
The ARP monitor (and ARP itself) may become confused by this
|
|
configuration, because ARP requests (generated by the ARP monitor)
|
|
will be sent on one interface (bond0), but the corresponding reply
|
|
will arrive on a different interface (eth0). This reply looks to ARP
|
|
as an unsolicited ARP reply (because ARP matches replies on an
|
|
interface basis), and is discarded. The MII monitor is not affected
|
|
by the state of the routing table.
|
|
|
|
The solution here is simply to insure that slaves do not have
|
|
routes of their own, and if for some reason they must, those routes do
|
|
not supercede routes of their master. This should generally be the
|
|
case, but unusual configurations or errant manual or automatic static
|
|
route additions may cause trouble.
|
|
|
|
9.2 Ethernet Device Renaming
|
|
----------------------------
|
|
|
|
On systems with network configuration scripts that do not
|
|
associate physical devices directly with network interface names (so
|
|
that the same physical device always has the same "ethX" name), it may
|
|
be necessary to add some special logic to either /etc/modules.conf or
|
|
/etc/modprobe.conf (depending upon which is installed on the system).
|
|
|
|
For example, given a modules.conf containing the following:
|
|
|
|
alias bond0 bonding
|
|
options bond0 mode=some-mode miimon=50
|
|
alias eth0 tg3
|
|
alias eth1 tg3
|
|
alias eth2 e1000
|
|
alias eth3 e1000
|
|
|
|
If neither eth0 and eth1 are slaves to bond0, then when the
|
|
bond0 interface comes up, the devices may end up reordered. This
|
|
happens because bonding is loaded first, then its slave device's
|
|
drivers are loaded next. Since no other drivers have been loaded,
|
|
when the e1000 driver loads, it will receive eth0 and eth1 for its
|
|
devices, but the bonding configuration tries to enslave eth2 and eth3
|
|
(which may later be assigned to the tg3 devices).
|
|
|
|
Adding the following:
|
|
|
|
add above bonding e1000 tg3
|
|
|
|
causes modprobe to load e1000 then tg3, in that order, when
|
|
bonding is loaded. This command is fully documented in the
|
|
modules.conf manual page.
|
|
|
|
On systems utilizing modprobe.conf (or modprobe.conf.local),
|
|
an equivalent problem can occur. In this case, the following can be
|
|
added to modprobe.conf (or modprobe.conf.local, as appropriate), as
|
|
follows (all on one line; it has been split here for clarity):
|
|
|
|
install bonding /sbin/modprobe tg3; /sbin/modprobe e1000;
|
|
/sbin/modprobe --ignore-install bonding
|
|
|
|
This will, when loading the bonding module, rather than
|
|
performing the normal action, instead execute the provided command.
|
|
This command loads the device drivers in the order needed, then calls
|
|
modprobe with --ignore-install to cause the normal action to then take
|
|
place. Full documentation on this can be found in the modprobe.conf
|
|
and modprobe manual pages.
|
|
|
|
9.3. Painfully Slow Or No Failed Link Detection By Miimon
|
|
---------------------------------------------------------
|
|
|
|
By default, bonding enables the use_carrier option, which
|
|
instructs bonding to trust the driver to maintain carrier state.
|
|
|
|
As discussed in the options section, above, some drivers do
|
|
not support the netif_carrier_on/_off link state tracking system.
|
|
With use_carrier enabled, bonding will always see these links as up,
|
|
regardless of their actual state.
|
|
|
|
Additionally, other drivers do support netif_carrier, but do
|
|
not maintain it in real time, e.g., only polling the link state at
|
|
some fixed interval. In this case, miimon will detect failures, but
|
|
only after some long period of time has expired. If it appears that
|
|
miimon is very slow in detecting link failures, try specifying
|
|
use_carrier=0 to see if that improves the failure detection time. If
|
|
it does, then it may be that the driver checks the carrier state at a
|
|
fixed interval, but does not cache the MII register values (so the
|
|
use_carrier=0 method of querying the registers directly works). If
|
|
use_carrier=0 does not improve the failover, then the driver may cache
|
|
the registers, or the problem may be elsewhere.
|
|
|
|
Also, remember that miimon only checks for the device's
|
|
carrier state. It has no way to determine the state of devices on or
|
|
beyond other ports of a switch, or if a switch is refusing to pass
|
|
traffic while still maintaining carrier on.
|
|
|
|
10. SNMP agents
|
|
===============
|
|
|
|
If running SNMP agents, the bonding driver should be loaded
|
|
before any network drivers participating in a bond. This requirement
|
|
is due to the the interface index (ipAdEntIfIndex) being associated to
|
|
the first interface found with a given IP address. That is, there is
|
|
only one ipAdEntIfIndex for each IP address. For example, if eth0 and
|
|
eth1 are slaves of bond0 and the driver for eth0 is loaded before the
|
|
bonding driver, the interface for the IP address will be associated
|
|
with the eth0 interface. This configuration is shown below, the IP
|
|
address 192.168.1.1 has an interface index of 2 which indexes to eth0
|
|
in the ifDescr table (ifDescr.2).
|
|
|
|
interfaces.ifTable.ifEntry.ifDescr.1 = lo
|
|
interfaces.ifTable.ifEntry.ifDescr.2 = eth0
|
|
interfaces.ifTable.ifEntry.ifDescr.3 = eth1
|
|
interfaces.ifTable.ifEntry.ifDescr.4 = eth2
|
|
interfaces.ifTable.ifEntry.ifDescr.5 = eth3
|
|
interfaces.ifTable.ifEntry.ifDescr.6 = bond0
|
|
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 5
|
|
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
|
|
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 4
|
|
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
|
|
|
|
This problem is avoided by loading the bonding driver before
|
|
any network drivers participating in a bond. Below is an example of
|
|
loading the bonding driver first, the IP address 192.168.1.1 is
|
|
correctly associated with ifDescr.2.
|
|
|
|
interfaces.ifTable.ifEntry.ifDescr.1 = lo
|
|
interfaces.ifTable.ifEntry.ifDescr.2 = bond0
|
|
interfaces.ifTable.ifEntry.ifDescr.3 = eth0
|
|
interfaces.ifTable.ifEntry.ifDescr.4 = eth1
|
|
interfaces.ifTable.ifEntry.ifDescr.5 = eth2
|
|
interfaces.ifTable.ifEntry.ifDescr.6 = eth3
|
|
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.10.10.10 = 6
|
|
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.1.1 = 2
|
|
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.10.74.20.94 = 5
|
|
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
|
|
|
|
While some distributions may not report the interface name in
|
|
ifDescr, the association between the IP address and IfIndex remains
|
|
and SNMP functions such as Interface_Scan_Next will report that
|
|
association.
|
|
|
|
11. Promiscuous mode
|
|
====================
|
|
|
|
When running network monitoring tools, e.g., tcpdump, it is
|
|
common to enable promiscuous mode on the device, so that all traffic
|
|
is seen (instead of seeing only traffic destined for the local host).
|
|
The bonding driver handles promiscuous mode changes to the bonding
|
|
master device (e.g., bond0), and propagates the setting to the slave
|
|
devices.
|
|
|
|
For the balance-rr, balance-xor, broadcast, and 802.3ad modes,
|
|
the promiscuous mode setting is propagated to all slaves.
|
|
|
|
For the active-backup, balance-tlb and balance-alb modes, the
|
|
promiscuous mode setting is propagated only to the active slave.
|
|
|
|
For balance-tlb mode, the active slave is the slave currently
|
|
receiving inbound traffic.
|
|
|
|
For balance-alb mode, the active slave is the slave used as a
|
|
"primary." This slave is used for mode-specific control traffic, for
|
|
sending to peers that are unassigned or if the load is unbalanced.
|
|
|
|
For the active-backup, balance-tlb and balance-alb modes, when
|
|
the active slave changes (e.g., due to a link failure), the
|
|
promiscuous setting will be propagated to the new active slave.
|
|
|
|
12. Configuring Bonding for High Availability
|
|
=============================================
|
|
|
|
High Availability refers to configurations that provide
|
|
maximum network availability by having redundant or backup devices,
|
|
links or switches between the host and the rest of the world. The
|
|
goal is to provide the maximum availability of network connectivity
|
|
(i.e., the network always works), even though other configurations
|
|
could provide higher throughput.
|
|
|
|
12.1 High Availability in a Single Switch Topology
|
|
--------------------------------------------------
|
|
|
|
If two hosts (or a host and a single switch) are directly
|
|
connected via multiple physical links, then there is no availability
|
|
penalty to optimizing for maximum bandwidth. In this case, there is
|
|
only one switch (or peer), so if it fails, there is no alternative
|
|
access to fail over to. Additionally, the bonding load balance modes
|
|
support link monitoring of their members, so if individual links fail,
|
|
the load will be rebalanced across the remaining devices.
|
|
|
|
See Section 13, "Configuring Bonding for Maximum Throughput"
|
|
for information on configuring bonding with one peer device.
|
|
|
|
12.2 High Availability in a Multiple Switch Topology
|
|
----------------------------------------------------
|
|
|
|
With multiple switches, the configuration of bonding and the
|
|
network changes dramatically. In multiple switch topologies, there is
|
|
a trade off between network availability and usable bandwidth.
|
|
|
|
Below is a sample network, configured to maximize the
|
|
availability of the network:
|
|
|
|
| |
|
|
|port3 port3|
|
|
+-----+----+ +-----+----+
|
|
| |port2 ISL port2| |
|
|
| switch A +--------------------------+ switch B |
|
|
| | | |
|
|
+-----+----+ +-----++---+
|
|
|port1 port1|
|
|
| +-------+ |
|
|
+-------------+ host1 +---------------+
|
|
eth0 +-------+ eth1
|
|
|
|
In this configuration, there is a link between the two
|
|
switches (ISL, or inter switch link), and multiple ports connecting to
|
|
the outside world ("port3" on each switch). There is no technical
|
|
reason that this could not be extended to a third switch.
|
|
|
|
12.2.1 HA Bonding Mode Selection for Multiple Switch Topology
|
|
-------------------------------------------------------------
|
|
|
|
In a topology such as the example above, the active-backup and
|
|
broadcast modes are the only useful bonding modes when optimizing for
|
|
availability; the other modes require all links to terminate on the
|
|
same peer for them to behave rationally.
|
|
|
|
active-backup: This is generally the preferred mode, particularly if
|
|
the switches have an ISL and play together well. If the
|
|
network configuration is such that one switch is specifically
|
|
a backup switch (e.g., has lower capacity, higher cost, etc),
|
|
then the primary option can be used to insure that the
|
|
preferred link is always used when it is available.
|
|
|
|
broadcast: This mode is really a special purpose mode, and is suitable
|
|
only for very specific needs. For example, if the two
|
|
switches are not connected (no ISL), and the networks beyond
|
|
them are totally independent. In this case, if it is
|
|
necessary for some specific one-way traffic to reach both
|
|
independent networks, then the broadcast mode may be suitable.
|
|
|
|
12.2.2 HA Link Monitoring Selection for Multiple Switch Topology
|
|
----------------------------------------------------------------
|
|
|
|
The choice of link monitoring ultimately depends upon your
|
|
switch. If the switch can reliably fail ports in response to other
|
|
failures, then either the MII or ARP monitors should work. For
|
|
example, in the above example, if the "port3" link fails at the remote
|
|
end, the MII monitor has no direct means to detect this. The ARP
|
|
monitor could be configured with a target at the remote end of port3,
|
|
thus detecting that failure without switch support.
|
|
|
|
In general, however, in a multiple switch topology, the ARP
|
|
monitor can provide a higher level of reliability in detecting end to
|
|
end connectivity failures (which may be caused by the failure of any
|
|
individual component to pass traffic for any reason). Additionally,
|
|
the ARP monitor should be configured with multiple targets (at least
|
|
one for each switch in the network). This will insure that,
|
|
regardless of which switch is active, the ARP monitor has a suitable
|
|
target to query.
|
|
|
|
|
|
13. Configuring Bonding for Maximum Throughput
|
|
==============================================
|
|
|
|
13.1 Maximizing Throughput in a Single Switch Topology
|
|
------------------------------------------------------
|
|
|
|
In a single switch configuration, the best method to maximize
|
|
throughput depends upon the application and network environment. The
|
|
various load balancing modes each have strengths and weaknesses in
|
|
different environments, as detailed below.
|
|
|
|
For this discussion, we will break down the topologies into
|
|
two categories. Depending upon the destination of most traffic, we
|
|
categorize them into either "gatewayed" or "local" configurations.
|
|
|
|
In a gatewayed configuration, the "switch" is acting primarily
|
|
as a router, and the majority of traffic passes through this router to
|
|
other networks. An example would be the following:
|
|
|
|
|
|
+----------+ +----------+
|
|
| |eth0 port1| | to other networks
|
|
| Host A +---------------------+ router +------------------->
|
|
| +---------------------+ | Hosts B and C are out
|
|
| |eth1 port2| | here somewhere
|
|
+----------+ +----------+
|
|
|
|
The router may be a dedicated router device, or another host
|
|
acting as a gateway. For our discussion, the important point is that
|
|
the majority of traffic from Host A will pass through the router to
|
|
some other network before reaching its final destination.
|
|
|
|
In a gatewayed network configuration, although Host A may
|
|
communicate with many other systems, all of its traffic will be sent
|
|
and received via one other peer on the local network, the router.
|
|
|
|
Note that the case of two systems connected directly via
|
|
multiple physical links is, for purposes of configuring bonding, the
|
|
same as a gatewayed configuration. In that case, it happens that all
|
|
traffic is destined for the "gateway" itself, not some other network
|
|
beyond the gateway.
|
|
|
|
In a local configuration, the "switch" is acting primarily as
|
|
a switch, and the majority of traffic passes through this switch to
|
|
reach other stations on the same network. An example would be the
|
|
following:
|
|
|
|
+----------+ +----------+ +--------+
|
|
| |eth0 port1| +-------+ Host B |
|
|
| Host A +------------+ switch |port3 +--------+
|
|
| +------------+ | +--------+
|
|
| |eth1 port2| +------------------+ Host C |
|
|
+----------+ +----------+port4 +--------+
|
|
|
|
|
|
Again, the switch may be a dedicated switch device, or another
|
|
host acting as a gateway. For our discussion, the important point is
|
|
that the majority of traffic from Host A is destined for other hosts
|
|
on the same local network (Hosts B and C in the above example).
|
|
|
|
In summary, in a gatewayed configuration, traffic to and from
|
|
the bonded device will be to the same MAC level peer on the network
|
|
(the gateway itself, i.e., the router), regardless of its final
|
|
destination. In a local configuration, traffic flows directly to and
|
|
from the final destinations, thus, each destination (Host B, Host C)
|
|
will be addressed directly by their individual MAC addresses.
|
|
|
|
This distinction between a gatewayed and a local network
|
|
configuration is important because many of the load balancing modes
|
|
available use the MAC addresses of the local network source and
|
|
destination to make load balancing decisions. The behavior of each
|
|
mode is described below.
|
|
|
|
|
|
13.1.1 MT Bonding Mode Selection for Single Switch Topology
|
|
-----------------------------------------------------------
|
|
|
|
This configuration is the easiest to set up and to understand,
|
|
although you will have to decide which bonding mode best suits your
|
|
needs. The trade offs for each mode are detailed below:
|
|
|
|
balance-rr: This mode is the only mode that will permit a single
|
|
TCP/IP connection to stripe traffic across multiple
|
|
interfaces. It is therefore the only mode that will allow a
|
|
single TCP/IP stream to utilize more than one interface's
|
|
worth of throughput. This comes at a cost, however: the
|
|
striping often results in peer systems receiving packets out
|
|
of order, causing TCP/IP's congestion control system to kick
|
|
in, often by retransmitting segments.
|
|
|
|
It is possible to adjust TCP/IP's congestion limits by
|
|
altering the net.ipv4.tcp_reordering sysctl parameter. The
|
|
usual default value is 3, and the maximum useful value is 127.
|
|
For a four interface balance-rr bond, expect that a single
|
|
TCP/IP stream will utilize no more than approximately 2.3
|
|
interface's worth of throughput, even after adjusting
|
|
tcp_reordering.
|
|
|
|
Note that this out of order delivery occurs when both the
|
|
sending and receiving systems are utilizing a multiple
|
|
interface bond. Consider a configuration in which a
|
|
balance-rr bond feeds into a single higher capacity network
|
|
channel (e.g., multiple 100Mb/sec ethernets feeding a single
|
|
gigabit ethernet via an etherchannel capable switch). In this
|
|
configuration, traffic sent from the multiple 100Mb devices to
|
|
a destination connected to the gigabit device will not see
|
|
packets out of order. However, traffic sent from the gigabit
|
|
device to the multiple 100Mb devices may or may not see
|
|
traffic out of order, depending upon the balance policy of the
|
|
switch. Many switches do not support any modes that stripe
|
|
traffic (instead choosing a port based upon IP or MAC level
|
|
addresses); for those devices, traffic flowing from the
|
|
gigabit device to the many 100Mb devices will only utilize one
|
|
interface.
|
|
|
|
If you are utilizing protocols other than TCP/IP, UDP for
|
|
example, and your application can tolerate out of order
|
|
delivery, then this mode can allow for single stream datagram
|
|
performance that scales near linearly as interfaces are added
|
|
to the bond.
|
|
|
|
This mode requires the switch to have the appropriate ports
|
|
configured for "etherchannel" or "trunking."
|
|
|
|
active-backup: There is not much advantage in this network topology to
|
|
the active-backup mode, as the inactive backup devices are all
|
|
connected to the same peer as the primary. In this case, a
|
|
load balancing mode (with link monitoring) will provide the
|
|
same level of network availability, but with increased
|
|
available bandwidth. On the plus side, active-backup mode
|
|
does not require any configuration of the switch, so it may
|
|
have value if the hardware available does not support any of
|
|
the load balance modes.
|
|
|
|
balance-xor: This mode will limit traffic such that packets destined
|
|
for specific peers will always be sent over the same
|
|
interface. Since the destination is determined by the MAC
|
|
addresses involved, this mode works best in a "local" network
|
|
configuration (as described above), with destinations all on
|
|
the same local network. This mode is likely to be suboptimal
|
|
if all your traffic is passed through a single router (i.e., a
|
|
"gatewayed" network configuration, as described above).
|
|
|
|
As with balance-rr, the switch ports need to be configured for
|
|
"etherchannel" or "trunking."
|
|
|
|
broadcast: Like active-backup, there is not much advantage to this
|
|
mode in this type of network topology.
|
|
|
|
802.3ad: This mode can be a good choice for this type of network
|
|
topology. The 802.3ad mode is an IEEE standard, so all peers
|
|
that implement 802.3ad should interoperate well. The 802.3ad
|
|
protocol includes automatic configuration of the aggregates,
|
|
so minimal manual configuration of the switch is needed
|
|
(typically only to designate that some set of devices is
|
|
available for 802.3ad). The 802.3ad standard also mandates
|
|
that frames be delivered in order (within certain limits), so
|
|
in general single connections will not see misordering of
|
|
packets. The 802.3ad mode does have some drawbacks: the
|
|
standard mandates that all devices in the aggregate operate at
|
|
the same speed and duplex. Also, as with all bonding load
|
|
balance modes other than balance-rr, no single connection will
|
|
be able to utilize more than a single interface's worth of
|
|
bandwidth.
|
|
|
|
Additionally, the linux bonding 802.3ad implementation
|
|
distributes traffic by peer (using an XOR of MAC addresses),
|
|
so in a "gatewayed" configuration, all outgoing traffic will
|
|
generally use the same device. Incoming traffic may also end
|
|
up on a single device, but that is dependent upon the
|
|
balancing policy of the peer's 8023.ad implementation. In a
|
|
"local" configuration, traffic will be distributed across the
|
|
devices in the bond.
|
|
|
|
Finally, the 802.3ad mode mandates the use of the MII monitor,
|
|
therefore, the ARP monitor is not available in this mode.
|
|
|
|
balance-tlb: The balance-tlb mode balances outgoing traffic by peer.
|
|
Since the balancing is done according to MAC address, in a
|
|
"gatewayed" configuration (as described above), this mode will
|
|
send all traffic across a single device. However, in a
|
|
"local" network configuration, this mode balances multiple
|
|
local network peers across devices in a vaguely intelligent
|
|
manner (not a simple XOR as in balance-xor or 802.3ad mode),
|
|
so that mathematically unlucky MAC addresses (i.e., ones that
|
|
XOR to the same value) will not all "bunch up" on a single
|
|
interface.
|
|
|
|
Unlike 802.3ad, interfaces may be of differing speeds, and no
|
|
special switch configuration is required. On the down side,
|
|
in this mode all incoming traffic arrives over a single
|
|
interface, this mode requires certain ethtool support in the
|
|
network device driver of the slave interfaces, and the ARP
|
|
monitor is not available.
|
|
|
|
balance-alb: This mode is everything that balance-tlb is, and more.
|
|
It has all of the features (and restrictions) of balance-tlb,
|
|
and will also balance incoming traffic from local network
|
|
peers (as described in the Bonding Module Options section,
|
|
above).
|
|
|
|
The only additional down side to this mode is that the network
|
|
device driver must support changing the hardware address while
|
|
the device is open.
|
|
|
|
13.1.2 MT Link Monitoring for Single Switch Topology
|
|
----------------------------------------------------
|
|
|
|
The choice of link monitoring may largely depend upon which
|
|
mode you choose to use. The more advanced load balancing modes do not
|
|
support the use of the ARP monitor, and are thus restricted to using
|
|
the MII monitor (which does not provide as high a level of end to end
|
|
assurance as the ARP monitor).
|
|
|
|
13.2 Maximum Throughput in a Multiple Switch Topology
|
|
-----------------------------------------------------
|
|
|
|
Multiple switches may be utilized to optimize for throughput
|
|
when they are configured in parallel as part of an isolated network
|
|
between two or more systems, for example:
|
|
|
|
+-----------+
|
|
| Host A |
|
|
+-+---+---+-+
|
|
| | |
|
|
+--------+ | +---------+
|
|
| | |
|
|
+------+---+ +-----+----+ +-----+----+
|
|
| Switch A | | Switch B | | Switch C |
|
|
+------+---+ +-----+----+ +-----+----+
|
|
| | |
|
|
+--------+ | +---------+
|
|
| | |
|
|
+-+---+---+-+
|
|
| Host B |
|
|
+-----------+
|
|
|
|
In this configuration, the switches are isolated from one
|
|
another. One reason to employ a topology such as this is for an
|
|
isolated network with many hosts (a cluster configured for high
|
|
performance, for example), using multiple smaller switches can be more
|
|
cost effective than a single larger switch, e.g., on a network with 24
|
|
hosts, three 24 port switches can be significantly less expensive than
|
|
a single 72 port switch.
|
|
|
|
If access beyond the network is required, an individual host
|
|
can be equipped with an additional network device connected to an
|
|
external network; this host then additionally acts as a gateway.
|
|
|
|
13.2.1 MT Bonding Mode Selection for Multiple Switch Topology
|
|
-------------------------------------------------------------
|
|
|
|
In actual practice, the bonding mode typically employed in
|
|
configurations of this type is balance-rr. Historically, in this
|
|
network configuration, the usual caveats about out of order packet
|
|
delivery are mitigated by the use of network adapters that do not do
|
|
any kind of packet coalescing (via the use of NAPI, or because the
|
|
device itself does not generate interrupts until some number of
|
|
packets has arrived). When employed in this fashion, the balance-rr
|
|
mode allows individual connections between two hosts to effectively
|
|
utilize greater than one interface's bandwidth.
|
|
|
|
13.2.2 MT Link Monitoring for Multiple Switch Topology
|
|
------------------------------------------------------
|
|
|
|
Again, in actual practice, the MII monitor is most often used
|
|
in this configuration, as performance is given preference over
|
|
availability. The ARP monitor will function in this topology, but its
|
|
advantages over the MII monitor are mitigated by the volume of probes
|
|
needed as the number of systems involved grows (remember that each
|
|
host in the network is configured with bonding).
|
|
|
|
14. Switch Behavior Issues
|
|
==========================
|
|
|
|
14.1 Link Establishment and Failover Delays
|
|
-------------------------------------------
|
|
|
|
Some switches exhibit undesirable behavior with regard to the
|
|
timing of link up and down reporting by the switch.
|
|
|
|
First, when a link comes up, some switches may indicate that
|
|
the link is up (carrier available), but not pass traffic over the
|
|
interface for some period of time. This delay is typically due to
|
|
some type of autonegotiation or routing protocol, but may also occur
|
|
during switch initialization (e.g., during recovery after a switch
|
|
failure). If you find this to be a problem, specify an appropriate
|
|
value to the updelay bonding module option to delay the use of the
|
|
relevant interface(s).
|
|
|
|
Second, some switches may "bounce" the link state one or more
|
|
times while a link is changing state. This occurs most commonly while
|
|
the switch is initializing. Again, an appropriate updelay value may
|
|
help.
|
|
|
|
Note that when a bonding interface has no active links, the
|
|
driver will immediately reuse the first link that goes up, even if the
|
|
updelay parameter has been specified (the updelay is ignored in this
|
|
case). If there are slave interfaces waiting for the updelay timeout
|
|
to expire, the interface that first went into that state will be
|
|
immediately reused. This reduces down time of the network if the
|
|
value of updelay has been overestimated, and since this occurs only in
|
|
cases with no connectivity, there is no additional penalty for
|
|
ignoring the updelay.
|
|
|
|
In addition to the concerns about switch timings, if your
|
|
switches take a long time to go into backup mode, it may be desirable
|
|
to not activate a backup interface immediately after a link goes down.
|
|
Failover may be delayed via the downdelay bonding module option.
|
|
|
|
14.2 Duplicated Incoming Packets
|
|
--------------------------------
|
|
|
|
It is not uncommon to observe a short burst of duplicated
|
|
traffic when the bonding device is first used, or after it has been
|
|
idle for some period of time. This is most easily observed by issuing
|
|
a "ping" to some other host on the network, and noticing that the
|
|
output from ping flags duplicates (typically one per slave).
|
|
|
|
For example, on a bond in active-backup mode with five slaves
|
|
all connected to one switch, the output may appear as follows:
|
|
|
|
# ping -n 10.0.4.2
|
|
PING 10.0.4.2 (10.0.4.2) from 10.0.3.10 : 56(84) bytes of data.
|
|
64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.7 ms
|
|
64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
|
|
64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
|
|
64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
|
|
64 bytes from 10.0.4.2: icmp_seq=1 ttl=64 time=13.8 ms (DUP!)
|
|
64 bytes from 10.0.4.2: icmp_seq=2 ttl=64 time=0.216 ms
|
|
64 bytes from 10.0.4.2: icmp_seq=3 ttl=64 time=0.267 ms
|
|
64 bytes from 10.0.4.2: icmp_seq=4 ttl=64 time=0.222 ms
|
|
|
|
This is not due to an error in the bonding driver, rather, it
|
|
is a side effect of how many switches update their MAC forwarding
|
|
tables. Initially, the switch does not associate the MAC address in
|
|
the packet with a particular switch port, and so it may send the
|
|
traffic to all ports until its MAC forwarding table is updated. Since
|
|
the interfaces attached to the bond may occupy multiple ports on a
|
|
single switch, when the switch (temporarily) floods the traffic to all
|
|
ports, the bond device receives multiple copies of the same packet
|
|
(one per slave device).
|
|
|
|
The duplicated packet behavior is switch dependent, some
|
|
switches exhibit this, and some do not. On switches that display this
|
|
behavior, it can be induced by clearing the MAC forwarding table (on
|
|
most Cisco switches, the privileged command "clear mac address-table
|
|
dynamic" will accomplish this).
|
|
|
|
15. Hardware Specific Considerations
|
|
====================================
|
|
|
|
This section contains additional information for configuring
|
|
bonding on specific hardware platforms, or for interfacing bonding
|
|
with particular switches or other devices.
|
|
|
|
15.1 IBM BladeCenter
|
|
--------------------
|
|
|
|
This applies to the JS20 and similar systems.
|
|
|
|
On the JS20 blades, the bonding driver supports only
|
|
balance-rr, active-backup, balance-tlb and balance-alb modes. This is
|
|
largely due to the network topology inside the BladeCenter, detailed
|
|
below.
|
|
|
|
JS20 network adapter information
|
|
--------------------------------
|
|
|
|
All JS20s come with two Broadcom Gigabit Ethernet ports
|
|
integrated on the planar (that's "motherboard" in IBM-speak). In the
|
|
BladeCenter chassis, the eth0 port of all JS20 blades is hard wired to
|
|
I/O Module #1; similarly, all eth1 ports are wired to I/O Module #2.
|
|
An add-on Broadcom daughter card can be installed on a JS20 to provide
|
|
two more Gigabit Ethernet ports. These ports, eth2 and eth3, are
|
|
wired to I/O Modules 3 and 4, respectively.
|
|
|
|
Each I/O Module may contain either a switch or a passthrough
|
|
module (which allows ports to be directly connected to an external
|
|
switch). Some bonding modes require a specific BladeCenter internal
|
|
network topology in order to function; these are detailed below.
|
|
|
|
Additional BladeCenter-specific networking information can be
|
|
found in two IBM Redbooks (www.ibm.com/redbooks):
|
|
|
|
"IBM eServer BladeCenter Networking Options"
|
|
"IBM eServer BladeCenter Layer 2-7 Network Switching"
|
|
|
|
BladeCenter networking configuration
|
|
------------------------------------
|
|
|
|
Because a BladeCenter can be configured in a very large number
|
|
of ways, this discussion will be confined to describing basic
|
|
configurations.
|
|
|
|
Normally, Ethernet Switch Modules (ESMs) are used in I/O
|
|
modules 1 and 2. In this configuration, the eth0 and eth1 ports of a
|
|
JS20 will be connected to different internal switches (in the
|
|
respective I/O modules).
|
|
|
|
A passthrough module (OPM or CPM, optical or copper,
|
|
passthrough module) connects the I/O module directly to an external
|
|
switch. By using PMs in I/O module #1 and #2, the eth0 and eth1
|
|
interfaces of a JS20 can be redirected to the outside world and
|
|
connected to a common external switch.
|
|
|
|
Depending upon the mix of ESMs and PMs, the network will
|
|
appear to bonding as either a single switch topology (all PMs) or as a
|
|
multiple switch topology (one or more ESMs, zero or more PMs). It is
|
|
also possible to connect ESMs together, resulting in a configuration
|
|
much like the example in "High Availability in a Multiple Switch
|
|
Topology," above.
|
|
|
|
Requirements for specific modes
|
|
-------------------------------
|
|
|
|
The balance-rr mode requires the use of passthrough modules
|
|
for devices in the bond, all connected to an common external switch.
|
|
That switch must be configured for "etherchannel" or "trunking" on the
|
|
appropriate ports, as is usual for balance-rr.
|
|
|
|
The balance-alb and balance-tlb modes will function with
|
|
either switch modules or passthrough modules (or a mix). The only
|
|
specific requirement for these modes is that all network interfaces
|
|
must be able to reach all destinations for traffic sent over the
|
|
bonding device (i.e., the network must converge at some point outside
|
|
the BladeCenter).
|
|
|
|
The active-backup mode has no additional requirements.
|
|
|
|
Link monitoring issues
|
|
----------------------
|
|
|
|
When an Ethernet Switch Module is in place, only the ARP
|
|
monitor will reliably detect link loss to an external switch. This is
|
|
nothing unusual, but examination of the BladeCenter cabinet would
|
|
suggest that the "external" network ports are the ethernet ports for
|
|
the system, when it fact there is a switch between these "external"
|
|
ports and the devices on the JS20 system itself. The MII monitor is
|
|
only able to detect link failures between the ESM and the JS20 system.
|
|
|
|
When a passthrough module is in place, the MII monitor does
|
|
detect failures to the "external" port, which is then directly
|
|
connected to the JS20 system.
|
|
|
|
Other concerns
|
|
--------------
|
|
|
|
The Serial Over LAN (SoL) link is established over the primary
|
|
ethernet (eth0) only, therefore, any loss of link to eth0 will result
|
|
in losing your SoL connection. It will not fail over with other
|
|
network traffic, as the SoL system is beyond the control of the
|
|
bonding driver.
|
|
|
|
It may be desirable to disable spanning tree on the switch
|
|
(either the internal Ethernet Switch Module, or an external switch) to
|
|
avoid fail-over delay issues when using bonding.
|
|
|
|
|
|
16. Frequently Asked Questions
|
|
==============================
|
|
|
|
1. Is it SMP safe?
|
|
|
|
Yes. The old 2.0.xx channel bonding patch was not SMP safe.
|
|
The new driver was designed to be SMP safe from the start.
|
|
|
|
2. What type of cards will work with it?
|
|
|
|
Any Ethernet type cards (you can even mix cards - a Intel
|
|
EtherExpress PRO/100 and a 3com 3c905b, for example). For most modes,
|
|
devices need not be of the same speed.
|
|
|
|
3. How many bonding devices can I have?
|
|
|
|
There is no limit.
|
|
|
|
4. How many slaves can a bonding device have?
|
|
|
|
This is limited only by the number of network interfaces Linux
|
|
supports and/or the number of network cards you can place in your
|
|
system.
|
|
|
|
5. What happens when a slave link dies?
|
|
|
|
If link monitoring is enabled, then the failing device will be
|
|
disabled. The active-backup mode will fail over to a backup link, and
|
|
other modes will ignore the failed link. The link will continue to be
|
|
monitored, and should it recover, it will rejoin the bond (in whatever
|
|
manner is appropriate for the mode). See the sections on High
|
|
Availability and the documentation for each mode for additional
|
|
information.
|
|
|
|
Link monitoring can be enabled via either the miimon or
|
|
arp_interval parameters (described in the module parameters section,
|
|
above). In general, miimon monitors the carrier state as sensed by
|
|
the underlying network device, and the arp monitor (arp_interval)
|
|
monitors connectivity to another host on the local network.
|
|
|
|
If no link monitoring is configured, the bonding driver will
|
|
be unable to detect link failures, and will assume that all links are
|
|
always available. This will likely result in lost packets, and a
|
|
resulting degradation of performance. The precise performance loss
|
|
depends upon the bonding mode and network configuration.
|
|
|
|
6. Can bonding be used for High Availability?
|
|
|
|
Yes. See the section on High Availability for details.
|
|
|
|
7. Which switches/systems does it work with?
|
|
|
|
The full answer to this depends upon the desired mode.
|
|
|
|
In the basic balance modes (balance-rr and balance-xor), it
|
|
works with any system that supports etherchannel (also called
|
|
trunking). Most managed switches currently available have such
|
|
support, and many unmanaged switches as well.
|
|
|
|
The advanced balance modes (balance-tlb and balance-alb) do
|
|
not have special switch requirements, but do need device drivers that
|
|
support specific features (described in the appropriate section under
|
|
module parameters, above).
|
|
|
|
In 802.3ad mode, it works with with systems that support IEEE
|
|
802.3ad Dynamic Link Aggregation. Most managed and many unmanaged
|
|
switches currently available support 802.3ad.
|
|
|
|
The active-backup mode should work with any Layer-II switch.
|
|
|
|
8. Where does a bonding device get its MAC address from?
|
|
|
|
If not explicitly configured (with ifconfig or ip link), the
|
|
MAC address of the bonding device is taken from its first slave
|
|
device. This MAC address is then passed to all following slaves and
|
|
remains persistent (even if the the first slave is removed) until the
|
|
bonding device is brought down or reconfigured.
|
|
|
|
If you wish to change the MAC address, you can set it with
|
|
ifconfig or ip link:
|
|
|
|
# ifconfig bond0 hw ether 00:11:22:33:44:55
|
|
|
|
# ip link set bond0 address 66:77:88:99:aa:bb
|
|
|
|
The MAC address can be also changed by bringing down/up the
|
|
device and then changing its slaves (or their order):
|
|
|
|
# ifconfig bond0 down ; modprobe -r bonding
|
|
# ifconfig bond0 .... up
|
|
# ifenslave bond0 eth...
|
|
|
|
This method will automatically take the address from the next
|
|
slave that is added.
|
|
|
|
To restore your slaves' MAC addresses, you need to detach them
|
|
from the bond (`ifenslave -d bond0 eth0'). The bonding driver will
|
|
then restore the MAC addresses that the slaves had before they were
|
|
enslaved.
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16. Resources and Links
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=======================
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The latest version of the bonding driver can be found in the latest
|
|
version of the linux kernel, found on http://kernel.org
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|
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|
The latest version of this document can be found in either the latest
|
|
kernel source (named Documentation/networking/bonding.txt), or on the
|
|
bonding sourceforge site:
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|
|
|
http://www.sourceforge.net/projects/bonding
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|
|
|
Discussions regarding the bonding driver take place primarily on the
|
|
bonding-devel mailing list, hosted at sourceforge.net. If you have
|
|
questions or problems, post them to the list. The list address is:
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|
|
|
bonding-devel@lists.sourceforge.net
|
|
|
|
The administrative interface (to subscribe or unsubscribe) can
|
|
be found at:
|
|
|
|
https://lists.sourceforge.net/lists/listinfo/bonding-devel
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|
|
|
Donald Becker's Ethernet Drivers and diag programs may be found at :
|
|
- http://www.scyld.com/network/
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|
|
|
You will also find a lot of information regarding Ethernet, NWay, MII,
|
|
etc. at www.scyld.com.
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-- END --
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