Linux Ethernet Bonding Driver HOWTO
Linux Ethernet Bonding Driver HOWTOLatest update: 21 June 2005
Initial release : Thomas Davis <tadavis at lbl.gov>Corrections, HA extensions : 2000/10/03-15 :
[*]Willy Tarreau <willy at meta-x.org>
[*]Constantine Gavrilov <const-g at xpert.com>
[*]Chad N. Tindel <ctindel at ieee dot org>
[*]Janice Girouard <girouard at us dot ibm dot com>
[*]Jay Vosburgh <fubar at us dot ibm dot com>
Reorganized and updated Feb 2005 by Jay Vosburgh
Introduction
The Linux bonding driver provides a method for aggregatingmultiple network interfaces into a single logical "bonded" interface.The behavior of the bonded interfaces depends upon the mode; generallyspeaking, modes provide either hot standby or load balancing services.Additionally, link integrity monitoring may be performed.
The bonding driver originally came from Donald Becker'sbeowulf patches for kernel 2.0. It has changed quite a bit since, andthe original tools from extreme-linux and beowulf sites will not workwith this version of the driver.
For new versions of the driver, updated userspace tools, andwho to ask for help, please follow the links at the end of this file.
Table of Contents
[*]Bonding Driver Installation
[*]Bonding Driver Options
[*]Configuring Bonding Devices3.1 Configuration with sysconfig support3.1.1 Using DHCP with sysconfig3.1.2 Configuring Multiple Bonds with sysconfig3.2 Configuration with initscripts support3.2.1 Using DHCP with initscripts3.2.2 Configuring Multiple Bonds with initscripts3.3 Configuring Bonding Manually3.3.1 Configuring Multiple Bonds Manually
[*]Querying Bonding Configuration5.1 Bonding Configuration5.2 Network Configuration
[*]Switch Configuration
[*]802.1q VLAN Support
[*]Link Monitoring8.1 ARP Monitor Operation8.2 Configuring Multiple ARP Targets8.3 MII Monitor Operation
[*]Potential Trouble Sources9.1 Adventures in Routing9.2 Ethernet Device Renaming9.3 Painfully Slow Or No Failed Link Detection By Miimon
[*]SNMP agents
[*]Promiscuous mode
[*]Configuring Bonding for High Availability12.1 High Availability in a Single Switch Topology12.2 High Availability in a Multiple Switch Topology12.2.1 HA Bonding Mode Selection for Multiple Switch Topology12.2.2 HA Link Monitoring for Multiple Switch Topology
[*]Configuring Bonding for Maximum Throughput13.1 Maximum Throughput in a Single Switch Topology13.1.1 MT Bonding Mode Selection for Single Switch Topology13.1.2 MT Link Monitoring for Single Switch Topology13.2 Maximum Throughput in a Multiple Switch Topology13.2.1 MT Bonding Mode Selection for Multiple Switch Topology13.2.2 MT Link Monitoring for Multiple Switch Topology
[*]Switch Behavior Issues14.1 Link Establishment and Failover Delays14.2 Duplicated Incoming Packets
[*]Hardware Specific Considerations15.1 IBM BladeCenter
[*]Frequently Asked Questions
[*]Resources and Links
1. Bonding Driver Installation
Most popular distro kernels ship with the bonding driveralready available as a module and the ifenslave user level controlprogram installed and ready for use. If your distro does not, or youhave need to compile bonding from source (e.g., configuring andinstalling a mainline kernel from kernel.org), you'll need to performthe following steps:
1.1 Configure and build the kernel with bonding
The current version of the bonding driver is available in thedrivers/net/bonding subdirectory of the most recent kernel source(which is available on http://kernel.org).Most users "rolling theirown" will want to use the most recent kernel from kernel.org.
Configure kernel with "make menuconfig" (or "make xconfig" or"make config"), then select "Bonding driver support" in the "Networkdevice support" section.It is recommended that you configure thedriver as module since it is currently the only way to pass parametersto the driver or configure more than one bonding device.
Build and install the new kernel and modules, then continuebelow to install ifenslave.
1.2 Install ifenslave Control Utility
The ifenslave user level control program is included in thekernel source tree, in the file Documentation/networking/ifenslave.c.It is generally recommended that you use the ifenslave thatcorresponds to the kernel that you are using (either from the samesource tree or supplied with the distro), however, ifenslaveexecutables from older kernels should function (but features newerthan the ifenslave release are not supported).Running an ifenslavethat is newer than the kernel is not supported, and may or may notwork.
To install ifenslave, do the following:
# gcc -Wall -O -I/usr/src/linux/include ifenslave.c -o ifenslave# cp ifenslave /sbin/ifenslave
If your kernel source is not in "/usr/src/linux," then replace"/usr/src/linux/include" in the above with the location of your kernelsource include directory.
You may wish to back up any existing /sbin/ifenslave, or, fortesting or informal use, tag the ifenslave to the kernel version(e.g., name the ifenslave executable /sbin/ifenslave-2.6.10).
IMPORTANT NOTE:
If you omit the "-I" or specify an incorrect directory, youmay end up with an ifenslave that is incompatible with the kernelyou're trying to build it for.Some distros (e.g., Red Hat from 7.1onwards) do not have /usr/include/linux symbolically linked to thedefault kernel source include directory.
2. Bonding Driver Options
Options for the bonding driver are supplied as parameters tothe bonding module at load time.They may be given as command linearguments to the insmod or modprobe command, but are usually specifiedin either the /etc/modules.conf or /etc/modprobe.conf configurationfile, or in a distro-specific configuration file (some of which aredetailed in the next section).
The available bonding driver parameters are listed below. If aparameter is not specified the default value is used.When initiallyconfiguring a bond, it is recommended "tail -f /var/log/messages" berun in a separate window to watch for bonding driver error messages.
It is critical that either the miimon or arp_interval andarp_ip_target parameters be specified, otherwise serious networkdegradation will occur during link failures.Very few devices do notsupport at least miimon, so there is really no reason not to use it.
Options with textual values will accept either the text nameor, for backwards compatibility, the option value.E.g.,"mode=802.3ad" and "mode=4" set the same mode.
The parameters are as follows:
arp_interval
Specifies the ARP link monitoring frequency in milliseconds. If ARP monitoring is used in an etherchannel compatible mode (modes 0 and 2), the switch should be configured in a mode that evenly distributes packets across all links. If the switch is configured to distribute the packets in an XOR fashion, all replies from the ARP targets will be received on the same link which could cause the other team members to fail.ARP monitoring should not be used in conjunction with miimon.A value of 0 disables ARP monitoring.The default value is 0.arp_ip_target
Specifies the IP addresses to use as ARP monitoring peers when arp_interval is > 0.These are the targets of the ARP request sent to determine the health of the link to the targets. Specify these values in ddd.ddd.ddd.ddd format.Multiple IP addresses must be separated by a comma.At least one IP address must be given for ARP monitoring to function.The maximum number of targets that can be specified is 16.The default value is no IP addresses.downdelay
Specifies the time, in milliseconds, to wait before disabling a slave after a link failure has been detected.This option is only valid for the miimon link monitor.The downdelay value should be a multiple of the miimon value; if not, it will be rounded down to the nearest multiple.The default value is 0.lacp_rate
Option specifying the rate in which we'll ask our link partner to transmit LACPDU packets in 802.3ad mode.Possible values are: slow or 0 Request partner to transmit LACPDUs every 30 seconds fast or 1 Request partner to transmit LACPDUs every 1 second The default is slow.max_bonds
Specifies the number of bonding devices to create for this instance of the bonding driver.E.g., if max_bonds is 3, and the bonding driver is not already loaded, then bond0, bond1 and bond2 will be created.The default value is 1.miimon
Specifies the MII link monitoring frequency in milliseconds. This determines how often the link state of each slave is inspected for link failures.A value of zero disables MII link monitoring.A value of 100 is a good starting point. The use_carrier option, below, affects how the link state is determined.See the High Availability section for additional information.The default value is 0.mode
Specifies one of the bonding policies. The default is balance-rr (round robin).Possible values are: balance-rr or 0 Round-robin policy: Transmit packets in sequential order from the first available slave through the last.This mode provides load balancing and fault tolerance. active-backup or 1 Active-backup policy: Only one slave in the bond is active.A different slave becomes active if, and only if, the active slave fails.The bond's MAC address is externally visible on only one port (network adapter) to avoid confusing the switch. In bonding version 2.6.2 or later, when a failover occurs in active-backup mode, bonding will issue one or more gratuitous ARPs on the newly active slave. One gratutious ARP is issued for the bonding master interface and each VLAN interfaces configured above it, provided that the interface has at least one IP address configured.Gratuitous ARPs issued for VLAN interfaces are tagged with the appropriate VLAN id. This mode provides fault tolerance.The primary option, documented below, affects the behavior of this mode. balance-xor or 2 XOR policy: Transmit based on the selected transmit hash policy.The default policy is a simple [(source MAC address XOR'd with destination MAC address) modulo slave count].Alternate transmit policies may be selected via the xmit_hash_policy option, described below. This mode provides load balancing and fault tolerance. broadcast or 3 Broadcast policy: transmits everything on all slave interfaces.This mode provides fault tolerance. 802.3ad or 4 IEEE 802.3ad Dynamic link aggregation.Creates aggregation groups that share the same speed and duplex settings.Utilizes all slaves in the active aggregator according to the 802.3ad specification. Slave selection for outgoing traffic is done according to the transmit hash policy, which may be changed from the default simple XOR policy via the xmit_hash_policy option, documented below.Note that not all transmit policies may be 802.3ad compliant, particularly in regards to the packet mis-ordering requirements of section 43.2.4 of the 802.3ad standard.Differing peer implementations will have varying tolerances for noncompliance. Prerequisites: 1. Ethtool support in the base drivers for retrieving the speed and duplex of each slave. 2. A switch that supports IEEE 802.3ad Dynamic link aggregation. Most switches will require some type of configuration to enable 802.3ad mode. balance-tlb or 5 Adaptive transmit load balancing: channel bonding that does not require any special switch support.The outgoing traffic is distributed according to the current load (computed relative to the speed) on each slave.Incoming traffic is received by the current slave.If the receiving slave fails, another slave takes over the MAC address of the failed receiving slave. Prerequisite: Ethtool support in the base drivers for retrieving the speed of each slave. balance-alb or 6 Adaptive load balancing: includes balance-tlb plus receive load balancing (rlb) for IPV4 traffic, and does not require any special switch support.The receive load balancing is achieved by ARP negotiation. The bonding driver intercepts the ARP Replies sent by the local system on their way out and overwrites the source hardware address with the unique hardware address of one of the slaves in the bond such that different peers use different hardware addresses for the server. Receive traffic from connections created by the server is also balanced.When the local system sends an ARP Request the bonding driver copies and saves the peer's IP information from the ARP packet.When the ARP Reply arrives from the peer, its hardware address is retrieved and the bonding driver initiates an ARP reply to this peer assigning it to one of the slaves in the bond.A problematic outcome of using ARP negotiation for balancing is that each time that an ARP request is broadcast it uses the hardware address of the bond.Hence, peers learn the hardware address of the bond and the balancing of receive traffic collapses to the current slave.This is handled by sending updates (ARP Replies) to all the peers with their individually assigned hardware address such that the traffic is redistributed.Receive traffic is also redistributed when a new slave is added to the bond and when an inactive slave is re-activated.The receive load is distributed sequentially (round robin) among the group of highest speed slaves in the bond. When a link is reconnected or a new slave joins the bond the receive traffic is redistributed among all active slaves in the bond by initiating ARP Replies with the selected mac address to each of the clients. The updelay parameter (detailed below) must be set to a value equal or greater than the switch's forwarding delay so that the ARP Replies sent to the peers will not be blocked by the switch. Prerequisites: 1. Ethtool support in the base drivers for retrieving the speed of each slave. 2. Base driver support for setting the hardware address of a device while it is open.This is required so that there will always be one slave in the team using the bond hardware address (the curr_active_slave) while having a unique hardware address for each slave in the bond.If the curr_active_slave fails its hardware address is swapped with the new curr_active_slave that was chosen.primary
A string (eth0, eth2, etc) specifying which slave is the primary device.The specified device will always be the active slave while it is available.Only when the primary is off-line will alternate devices be used.This is useful when one slave is preferred over another, e.g., when one slave has higher throughput than another. The primary option is only valid for active-backup mode.updelay
Specifies the time, in milliseconds, to wait before enabling a slave after a link recovery has been detected.This option is only valid for the miimon link monitor.The updelay value should be a multiple of the miimon value; if not, it will be rounded down to the nearest multiple.The default value is 0.use_carrier
Specifies whether or not miimon should use MII or ETHTOOL ioctls vs. netif_carrier_ok() to determine the link status. The MII or ETHTOOL ioctls are less efficient and utilize a deprecated calling sequence within the kernel.The netif_carrier_ok() relies on the device driver to maintain its state with netif_carrier_on/off; at this writing, most, but not all, device drivers support this facility. If bonding insists that the link is up when it should not be, it may be that your network device driver does not support netif_carrier_on/off.The default state for netif_carrier is "carrier on," so if a driver does not support netif_carrier, it will appear as if the link is always up.In this case, setting use_carrier to 0 will cause bonding to revert to the MII / ETHTOOL ioctl method to determine the link state. A value of 1 enables the use of netif_carrier_ok(), a value of 0 will use the deprecated MII / ETHTOOL ioctls.The default value is 1.xmit_hash_policy
Selects the transmit hash policy to use for slave selection in balance-xor and 802.3ad modes.Possible values are: layer2 Uses XOR of hardware MAC addresses to generate the hash.The formula is (source MAC XOR destination MAC) modulo slave count This algorithm will place all traffic to a particular network peer on the same slave. This algorithm is 802.3ad compliant. layer3+4 This policy uses upper layer protocol information, when available, to generate the hash.This allows for traffic to a particular network peer to span multiple slaves, although a single connection will not span multiple slaves. The formula for unfragmented TCP and UDP packets is ((source port XOR dest port) XOR ((source IP XOR dest IP) AND 0xffff) modulo slave count For fragmented TCP or UDP packets and all other IP protocol traffic, the source and destination port information is omitted.For non-IP traffic, the formula is the same as for the layer2 transmit hash policy. This policy is intended to mimic the behavior of certain switches, notably Cisco switches with PFC2 as well as some Foundry and IBM products. This algorithm is not fully 802.3ad compliant.A single TCP or UDP conversation containing both fragmented and unfragmented packets will see packets striped across two interfaces.This may result in out of order delivery.Most traffic types will not meet this criteria, as TCP rarely fragments traffic, and most UDP traffic is not involved in extended conversations.Other implementations of 802.3ad may or may not tolerate this noncompliance. The default value is layer2.This option was added in bondingversion 2.6.3.In earlier versions of bonding, this parameter doesnot exist, and the layer2 policy is the only policy.
3. Configuring Bonding Devices
There are, essentially, two methods for configuring bonding:with support from the distro's network initialization scripts, andwithout.Distros generally use one of two packages for the networkinitialization scripts: initscripts or sysconfig.Recent versions ofthese packages have support for bonding, while older versions do not.
We will first describe the options for configuring bonding fordistros using versions of initscripts and sysconfig with full orpartial support for bonding, then provide information on enablingbonding without support from the network initialization scripts (i.e.,older versions of initscripts or sysconfig).
If you're unsure whether your distro uses sysconfig orinitscripts, or don't know if it's new enough, have no fear.Determining this is fairly straightforward.
First, issue the command:
$ rpm -qf /sbin/ifup
It will respond with a line of text starting with either"initscripts" or "sysconfig," followed by some numbers.This is thepackage that provides your network initialization scripts.
Next, to determine if your installation supports bonding,issue the command:
$ grep ifenslave /sbin/ifup
If this returns any matches, then your initscripts orsysconfig has support for bonding.
3.1 Configuration with sysconfig support
This section applies to distros using a version of sysconfigwith bonding support, for example, SuSE Linux Enterprise Server 9.
SuSE SLES 9's networking configuration system does supportbonding, however, at this writing, the YaST system configurationfrontend 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 theslave devices.On SLES 9, this is most easily done by running theyast2 sysconfig configuration utility.The goal is for to create anifcfg-id file for each slave device.The simplest way to accomplishthis is to configure the devices for DHCP (this is only to get thefile ifcfg-id file created; see below for some issues with DHCP).Thename 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 fromthe device's permanent MAC address.
Once the set of ifcfg-id-xx:xx:xx:xx:xx:xx files has beencreated, it is necessary to edit the configuration files for the slavedevices (the MAC addresses correspond to those of the slave devices).Before editing, the file will contain multiple lines, and will looksomething 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 otherlines (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 deviceitself.This file is named ifcfg-bondX, where X is the number of thebonding device to create, starting at 0.The first such file isifcfg-bond0, the second is ifcfg-bond1, and so on.The sysconfignetwork configuration system will correctly start multiple instancesof 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 NETWORKvalues 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<script type="text/javascript">&lt;!--google_ad_client = &quot;pub-7825705102693166&quot;;google_alternate_ad_url = &quot;http://www.cyberciti.biz/noads.html&quot;;google_ad_width = 728;google_ad_height = 90;google_ad_format = &quot;728x90_as&quot;;google_ad_type = &quot;text_image&quot;;google_color_border = &quot;FFFFFF&quot;;google_color_bg = &quot;FFFFFF&quot;;google_color_link = &quot;0000FF&quot;;google_color_url = &quot;008000&quot;;google_color_text = &quot;000000&quot;;//--&gt;</script><script src="http://pagead2.googlesyndication.com/pagead/show_ads.js" type="text/javascript"></script><script>google_protectAndRun(&quot;ads_core.google_render_ad&quot;, google_handleError, google_render_ad);</script>bonding master device.The only useful value is "yes."
The contents of BONDING_MODULE_OPTS are supplied to theinstance of the bonding module for this device.Specify the optionsfor the bonding mode, link monitoring, and so on here.Do not includethe max_bonds bonding parameter; this will confuse the configurationsystem if you have multiple bonding devices.
Finally, supply one BONDING_SLAVEn="slave device" for eachslave.where "n" is an increasing value, one for each slave.The"slave device" is either an interface name, e.g., "eth0", or a devicespecifier for the network device.The interface name is easier tofind, 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 physicalnetwork device, and will not change unless the device's bus locationchanges (for example, it is moved from one PCI slot to another).Theexample above uses one of each type for demonstration purposes; mostconfigurations 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 takeeffect.This can be accomplished via the following:
# /etc/init.d/network restart
Note that the network control script (/sbin/ifdown) willremove the bonding module as part of the network shutdown processing,so it is not necessary to remove the module by hand if, e.g., themodule parameters have changed.
Also, at this writing, YaST/YaST2 will not manage bondingdevices (they do not show bonding interfaces on its list of networkdevices).It is necessary to edit the configuration file by hand tochange the bonding configuration.
Additional general options and details of the ifcfg fileformat 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 thiswriting, this does not function for bonding devices; the scriptsattempt to obtain the device address from DHCP prior to adding any ofthe slave devices.Without active slaves, the DHCP requests are notsent to the network.
3.1.2 Configuring Multiple Bonds with sysconfig
The sysconfig network initialization system is capable ofhandling multiple bonding devices.All that is necessary is for eachbonding instance to have an appropriately configured ifcfg-bondX file(as described above).Do not specify the "max_bonds" parameter to anyinstance of bonding, as this will confuse sysconfig.If you requiremultiple bonding devices with identical parameters, create multipleifcfg-bondX files.
Because the sysconfig scripts supply the bonding moduleoptions in the ifcfg-bondX file, it is not necessary to add them tothe 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 initscriptswith bonding support, for example, Red Hat Linux 9 or Red HatEnterprise Linux version 3 or 4.On these systems, the networkinitialization scripts have some knowledge of bonding, and can beconfigured to control bonding devices.
These distros will not automatically load the network adapterdriver unless the ethX device is configured with an IP address.Because of this constraint, users must manually configure anetwork-script file for all physical adapters that will be members ofa bondX link.Network script files are located in the directory:
/etc/sysconfig/network-scripts
The file name must be prefixed with "ifcfg-eth" and suffixedwith the adapter's physical adapter number.For example, the scriptfor 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 andmust correspond with the name of the file, i.e., ifcfg-eth1 must havea device line of DEVICE=eth1.The setting of the MASTER= line willalso depend on the final bonding interface name chosen for your bond.As with other network devices, these typically start at 0, and go upone for each device, i.e., the first bonding instance is bond0, thesecond is bond1, and so on.
Next, create a bond network script.The file name for thisscript will be /etc/sysconfig/network-scripts/ifcfg-bondX where X isthe 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 bondingmodule with your desired options when the bond0 interface is broughtup.The following lines in /etc/modules.conf (or modprobe.conf) willload 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 ofoptions for your configuration.
Finally run "/etc/rc.d/init.d/network restart" as root.Thiswill restart the networking subsystem and your bond link should be nowup and running.
3.2.1 Using DHCP with initscripts
Recent versions of initscripts (the version supplied withFedora Core 3 and Red Hat Enterprise Linux 4 is reported to work) dohave support for assigning IP information to bonding devices via DHCP.
To configure bonding for DHCP, configure it as describedabove, except replace the line "BOOTPROTO=none" with "BOOTPROTO=dhcp"and add a line consisting of "TYPE=Bonding".Note that the TYPE valueis case sensitive.
3.2.2 Configuring Multiple Bonds with initscripts
At this writing, the initscripts package does not directlysupport loading the bonding driver multiple times, so the process fordoing so is the same as described in the "Configuring Multiple BondsManually" section, below.
NOTE: It has been observed that some Red Hat supplied kernelsare apparently unable to rename modules at load time (the "-o bond1"part).Attempts to pass that option to modprobe will produce an"Operation not permitted" error.This has been reported on someFedora Core kernels, and has been seen on RHEL 4 as well.On kernelsexhibiting this problem, it will be impossible to configure multiplebonds with differing parameters.
<script type="text/javascript">&lt;!--google_ad_client = &quot;pub-7825705102693166&quot;;google_alternate_ad_url = &quot;http://www.cyberciti.biz/noads.html&quot;;google_ad_width = 728;google_ad_height = 90;google_ad_format = &quot;728x90_as&quot;;google_ad_type = &quot;text_image&quot;;google_color_border = &quot;FFFFFF&quot;;google_color_bg = &quot;FFFFFF&quot;;google_color_link = &quot;0000FF&quot;;google_color_url = &quot;008000&quot;;google_color_text = &quot;000000&quot;;//--&gt;</script><script src="http://pagead2.googlesyndication.com/pagead/show_ads.js" type="text/javascript"></script><script>google_protectAndRun(&quot;ads_core.google_render_ad&quot;, google_handleError, google_render_ad);</script>3.3 Configuring Bonding Manually
This section applies to distros whose network initializationscripts (the sysconfig or initscripts package) do not have specificknowledge of bonding.One such distro is SuSE Linux Enterprise Serverversion 8.
The general method for these systems is to place the bondingmodule parameters into /etc/modules.conf or /etc/modprobe.conf (asappropriate for the installed distro), then add modprobe and/orifenslave commands to the system's global init script.The name ofthe 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 e100devices (presumed to be eth0 and eth1), and have it persist acrossreboots, 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=100modprobe e100
ifconfig bond0 192.168.1.1 netmask 255.255.255.0 upifenslave bond0 eth0
ifenslave bond0 eth1
Replace the example bonding module parameters and bond0network configuration (IP address, netmask, etc) with the appropriatevalues for your configuration.
Unfortunately, this method will not provide support for theifup and ifdown scripts on the bond devices.To reload the bondingconfiguration, 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 scriptwhich only initializes the bonding configuration, then call thatseparate script from within boot.local.This allows for bonding to beenabled without re-running the entire global init script.
To shut down the bonding devices, it is necessary to firstmark the bonding device itself as being down, then remove theappropriate device driver modules.For our example above, you can dothe following:
# ifconfig bond0 down
# rmmod bonding
# rmmod e100
Again, for convenience, it may be desirable to create a scriptwith these commands.
3.3.1 Configuring Multiple Bonds Manually
This section contains information on configuring multiplebonding devices with differing options for those systems whose networkinitialization scripts lack support for configuring multiple bonds.
If you require multiple bonding devices, but all with the sameoptions, you may wish to use the "max_bonds" module parameter,documented above.
To create multiple bonding devices with differing options, itis necessary to load the bonding driver multiple times.Note thatcurrent versions of the sysconfig network initialization scriptshandle this automatically; if your distro uses these scripts, nospecial action is needed.See the section Configuring BondingDevices, above, if you're not sure about your network initializationscripts.
To load multiple instances of the module, it is necessary tospecify a different name for each instance (the module loading systemrequires that every loaded module, even multiple instances of the samemodule, have a unique name).This is accomplished by supplyingmultiple 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 isnamed "bond0" and creates the bond0 device in balance-rr mode with anmiimon of 100.The second instance is named "bond1" and creates thebond1 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 seesits options.In that case, the second options line can be substitutedas follows:
install bond1 /sbin/modprobe --ignore-install bonding -o bond1 \
mode=balance-alb miimon=50
This may be repeated any number of times, specifying a new andunique 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 informationabout the bonding configuration, options and state of each slave.
For example, the contents of /proc/net/bonding/bond0 after thedriver is loaded with parameters of mode=0 and miimon=1000 isgenerally 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 thebonding configuration, state, and version of the bonding driver.
5.2 Network configuration
The network configuration can be inspected using the ifconfigcommand.Bonding devices will have the MASTER flag set; Bonding slavedevices will have the SLAVE flag set.The ifconfig output does notcontain 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 ofbond0 have the same MAC address (HWaddr) as bond0 for all modes exceptTLB and ALB that require a unique MAC address for each slave.
# /sbin/ifconfig
bond0 Link encap:EthernetHWaddr 00:C0:F0:1F:37:B4 inet addr:XXX.XXX.XXX.YYYBcast:XXX.XXX.XXX.255Mask:255.255.252.0 UP BROADCAST RUNNING MASTER MULTICASTMTU:1500Metric: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:0eth0 Link encap:EthernetHWaddr 00:C0:F0:1F:37:B4 inet addr:XXX.XXX.XXX.YYYBcast:XXX.XXX.XXX.255Mask:255.255.252.0 UP BROADCAST RUNNING SLAVE MULTICASTMTU:1500Metric: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:0x1080eth1 Link encap:EthernetHWaddr 00:C0:F0:1F:37:B4 inet addr:XXX.XXX.XXX.YYYBcast:XXX.XXX.XXX.255Mask:255.255.252.0 UP BROADCAST RUNNING SLAVE MULTICASTMTU:1500Metric: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:0x14006. Switch Configuration
For this section, "switch" refers to whatever system thebonded devices are directly connected to (i.e., where the other end ofthe cable plugs into).This may be an actual dedicated switch device,or it may be another regular system (e.g., another computer runningLinux),
The active-backup, balance-tlb and balance-alb modes do notrequire any specific configuration of the switch.
The 802.3ad mode requires that the switch have the appropriateports configured as an 802.3ad aggregation.The precise method usedto configure this varies from switch to switch, but, for example, aCisco 3550 series switch requires that the appropriate ports first begrouped together in a single etherchannel instance, then thatetherchannel is set to mode "lacp" to enable 802.3ad (instead ofstandard EtherChannel).
The balance-rr, balance-xor and broadcast modes generallyrequire that the switch have the appropriate ports grouped together.The nomenclature for such a group differs between switches, it may becalled an "etherchannel" (as in the Cisco example, above), a "trunkgroup" or some other similar variation.For these modes, each switchwill also have its own configuration options for the switch's transmitpolicy to the bond.Typical choices include XOR of either the MAC orIP addresses.The transmit policy of the two peers does not need tomatch.For these three modes, the bonding mode really selects atransmit policy for an EtherChannel group; all three will interoperatewith another EtherChannel group.
7. 802.1q VLAN Support
It is possible to configure VLAN devices over a bond interfaceusing the 8021q driver.However, only packets coming from the 8021qdriver and passing through bonding will be tagged by default.Selfgenerated packets, for example, bonding's learning packets or ARPpackets generated by either ALB mode or the ARP monitor mechanism, aretagged internally by bonding itself.As a result, bonding must"learn" the VLAN IDs configured above it, and use those IDs to tagself generated packets.
For reasons of simplicity, and to support the use of adaptersthat can do VLAN hardware acceleration offloading, the bondinginterface declares itself as fully hardware offloading capable, it getsthe add_vid/kill_vid notifications to gather the necessaryinformation, and it propagates those actions to the slaves.In caseof mixed adapter types, hardware accelerated tagged packets thatshould go through an adapter that is not offloading capable are"un-accelerated" by the bonding driver so the VLAN tag sits in theregular location.
VLAN interfaces must be added on top of a bonding interfaceonly after enslaving at least one slave.The bonding interface has ahardware 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, itwould pick up the all-zeroes hardware address.Once the first slaveis attached to the bond, the bond device itself will pick up theslave's hardware address, which is then available for the VLAN device.
Also, be aware that a similar problem can occur if all slavesare released from a bond that still has one or more VLAN interfaces ontop of it.When a new slave is added, the bonding interface willobtain its hardware address from the first slave, which might notmatch the hardware address of the VLAN interfaces (which wasultimately copied from an earlier slave).
There are two methods to insure that the VLAN device operateswith the correct hardware address if all slaves are removed from abond interface:
[*]Remove all VLAN interfaces then recreate them
[*]Set the bonding interface's hardware address so that itmatches the hardware address of the VLAN interfaces.
Note that changing a VLAN interface's HW address would set theunderlying device -- i.e. the bonding interface -- to promiscuousmode, which might not be what you want.
8. Link Monitoring
The bonding driver at present supports two schemes formonitoring a slave device's link state: the ARP monitor and the MIImonitor.
At the present time, due to implementation restrictions in thebonding driver itself, it is not possible to enable both ARP and MIImonitoring simultaneously.
8.1 ARP Monitor Operation
The ARP monitor operates as its name suggests: it sends ARPqueries to one or more designated peer systems on the network, anduses the response as an indication that the link is operating.Thisgives some assurance that traffic is actually flowing to and from oneor more peers on the local network.
The ARP monitor relies on the device driver itself to verifythat traffic is flowing.In particular, the driver must keep up todate the last receive time, dev->last_rx, and transmit start time,dev->trans_start.If these are not updated by the driver, then theARP monitor will immediately fail any slaves using that driver, andthose slaves will stay down.If networking monitoring (tcpdump, etc)shows the ARP requests and replies on the network, then it may be thatyour 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 canbe useful in a High Availability setup to have several targets tomonitor.In the case of just one target, the target itself may godown or have a problem making it unresponsive to ARP requests.Havingan additional target (or several) increases the reliability of the ARPmonitoring.
Multiple ARP targets must be separated by commas as follows:
# example options for ARP monitoring with three targetsalias 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 targetalias 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 localnetwork interface.It accomplishes this in one of three ways: bydepending upon the device driver to maintain its carrier state, byquerying the device's MII registers, or by making an ethtool query tothe device.
If the use_carrier module parameter is 1 (the default value),then the MII monitor will rely on the driver for carrier stateinformation (via the netif_carrier subsystem).As explained in theuse_carrier parameter information, above, if the MII monitor fails todetect carrier loss on the device (e.g., when the cable is physicallydisconnected), it may be that the driver does not supportnetif_carrier.
If use_carrier is 0, then the MII monitor will first query thedevice's (via ioctl) MII registers and check the link state.If thatrequest fails (not just that it returns carrier down), then the MIImonitor will make an ethtool ETHOOL_GLINK request to attempt to obtainthe same information.If both methods fail (i.e., the driver eitherdoes not support or had some error in processing both the MII registerand ethtool requests), then the MII monitor will assume the link isup.
9. Potential Sources of Trouble
9.1 Adventures in Routing
When bonding is configured, it is important that the slavedevices not have routes that supercede routes of the master (or,generally, not have routes at all).For example, suppose the bondingdevice bond0 has two slaves, eth0 and eth1, and the routing table isas follows:
Kernel IP routing table
Destination Gateway Genmask Flags MSS Windowirtt Iface10.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth010.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 eth110.0.0.0 0.0.0.0 255.255.0.0 U 40 0 0 bond0127.0.0.0 0.0.0.0 255.0.0.0 U 40 0 0 lo This routing configuration will likely still update thereceive/transmit times in the driver (needed by the ARP monitor), butmay bypass the bonding driver (because outgoing traffic to, in thiscase, another host on network 10 would use eth0 or eth1 before bond0).
The ARP monitor (and ARP itself) may become confused by thisconfiguration, because ARP requests (generated by the ARP monitor)will be sent on one interface (bond0), but the corresponding replywill arrive on a different interface (eth0).This reply looks to ARPas an unsolicited ARP reply (because ARP matches replies on aninterface basis), and is discarded.The MII monitor is not affectedby the state of the routing table.
The solution here is simply to insure that slaves do not haveroutes of their own, and if for some reason they must, those routes donot supercede routes of their master.This should generally be thecase, but unusual configurations or errant manual or automatic staticroute additions may cause trouble.
9.2 Ethernet Device Renaming
On systems with network configuration scripts that do notassociate physical devices directly with network interface names (sothat the same physical device always has the same "ethX" name), it maybe 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 thebond0 interface comes up, the devices may end up reordered.Thishappens because bonding is loaded first, then its slave device'sdrivers are loaded next.Since no other drivers have been loaded,when the e1000 driver loads, it will receive eth0 and eth1 for itsdevices, 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, whenbonding is loaded.This command is fully documented in themodules.conf manual page.
On systems utilizing modprobe.conf (or modprobe.conf.local),an equivalent problem can occur.In this case, the following can beadded to modprobe.conf (or modprobe.conf.local, as appropriate), asfollows (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 thanperforming the normal action, instead execute the provided command.This command loads the device drivers in the order needed, then callsmodprobe with --ignore-install to cause the normal action to then takeplace.Full documentation on this can be found in the modprobe.confand modprobe manual pages.
9.3. Painfully Slow Or No Failed Link Detection By Miimon
By default, bonding enables the use_carrier option, whichinstructs bonding to trust the driver to maintain carrier state.
As discussed in the options section, above, some drivers donot 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 donot maintain it in real time, e.g., only polling the link state atsome fixed interval.In this case, miimon will detect failures, butonly after some long period of time has expired.If it appears thatmiimon is very slow in detecting link failures, try specifyinguse_carrier=0 to see if that improves the failure detection time.Ifit does, then it may be that the driver checks the carrier state at afixed interval, but does not cache the MII register values (so theuse_carrier=0 method of querying the registers directly works).Ifuse_carrier=0 does not improve the failover, then the driver may cachethe registers, or the problem may be elsewhere.
Also, remember that miimon only checks for the device'scarrier state.It has no way to determine the state of devices on orbeyond other ports of a switch, or if a switch is refusing to passtraffic while still maintaining carrier on.
10. SNMP agents
If running SNMP agents, the bonding driver should be loadedbefore any network drivers participating in a bond.This requirementis due to the interface index (ipAdEntIfIndex) being associated tothe first interface found with a given IP address.That is, there isonly one ipAdEntIfIndex for each IP address.For example, if eth0 andeth1 are slaves of bond0 and the driver for eth0 is loaded before thebonding driver, the interface for the IP address will be associatedwith the eth0 interface.This configuration is shown below, the IPaddress 192.168.1.1 has an interface index of 2 which indexes to eth0in 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 beforeany network drivers participating in a bond.Below is an example ofloading the bonding driver first, the IP address 192.168.1.1 iscorrectly 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 inifDescr, the association between the IP address and IfIndex remainsand SNMP functions such as Interface_Scan_Next will report thatassociation.
11. Promiscuous mode
When running network monitoring tools, e.g., tcpdump, it iscommon to enable promiscuous mode on the device, so that all trafficis seen (instead of seeing only traffic destined for the local host).The bonding driver handles promiscuous mode changes to the bondingmaster device (e.g., bond0), and propagates the setting to the slavedevices.
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, thepromiscuous mode setting is propagated only to the active slave.
For balance-tlb mode, the active slave is the slave currentlyreceiving 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, forsending to peers that are unassigned or if the load is unbalanced.
For the active-backup, balance-tlb and balance-alb modes, whenthe active slave changes (e.g., due to a link failure), thepromiscuous setting will be propagated to the new active slave.
12. Configuring Bonding for High Availability
High Availability refers to configurations that providemaximum network availability by having redundant or backup devices,links or switches between the host and the rest of the world.Thegoal is to provide the maximum availability of network connectivity(i.e., the network always works), even though other configurationscould provide higher throughput.
12.1 High Availability in a Single Switch Topology
If two hosts (or a host and a single switch) are directlyconnected via multiple physical links, then there is no availabilitypenalty to optimizing for maximum bandwidth.In this case, there isonly one switch (or peer), so if it fails, there is no alternativeaccess to fail over to.Additionally, the bonding load balance modessupport 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 thenetwork changes dramatically.In multiple switch topologies, there isa trade off between network availability and usable bandwidth.
Below is a sample network, configured to maximize theavailability 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 twoswitches (ISL, or inter switch link), and multiple ports connecting tothe outside world ("port3" on each switch).There is no technicalreason 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 andbroadcast modes are the only useful bonding modes when optimizing for
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