Red Hat Enterprise Linux 3 Channel Bonding Interfaces

Issue:

How can I bond multiple network interfaces (bonding) together into a single channel in Red Hat Enterprise Linux 3?

Resolution:

Red Hat Enterprise Linux allows administrators to bind multiple network interfaces together into a single channel using the bonding kernel module and a special network interface called a channel bonding interface. Channel bonding enables two or more network interfaces to act as one, simultaneously, increasing the bandwidth and providing redundancy.

To create a channel bonding interface, create a file in the /etc/sysconfig/network-scripts/ directory called ifcfg-bond , replacing with the number for the interface, such as 0.

The contents of the file can be identical to whatever type of interface that is getting bonded, such as an Ethernet interface. The only difference is that the DEVICE= directive must be bond , replacing with the number for the interface.

The following is a sample channel bonding configuration file:

DEVICE=bond0
BOOTPROTO=none
ONBOOT=yes
NETWORK=10.0.1.0
NETMASK=255.255.255.0
IPADDR=10.0.1.27
USERCTL=no


After the channel bonding interfaces are created, the network interfaces to be bound together must be configured by adding the MASTER= and SLAVE= directives to their configuration files. The configuration files for each of the channel bonded interfaces can be nearly identical.

For example, if channel bonding two Ethernet interfaces, both eth0 and eth1 may look like the following example:

DEVICE=eth
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes
USERCTL=no


In this example, replace with the numerical value for the interface.

For a channel bonding interface to be valid, the kernel module must be loaded. The procedure for loading the module is slightly different on Red Enterprise Linux Version 3 and Red Hat Enterprise Linux Version 4.

Red Hat Enterprise Linux Version 3
To ensure that the module is loaded when the channel bonding interface is brought up, add the following line to /etc/modules.conf:

alias bond bondingReplace with the number of the interface, such as 0. For bonded aliases other than bond0 a line is also needed such as:

options bond -o bonding For each configured channel bonding interface, there must be a corresponding entry in /etc/modules.conf.

Once /etc/modules.conf is configured and the channel bonding interface and network interfaces are configured, the ifup command can be used to bring up the channel bonding interface or you can simply restart your networking services with service network restart.

Additional Information: Important aspects of the channel bonding interface are controlled through the kernel module.



mode= — Specifies one of four policies allowed for the bonding module. Acceptable values for this parameter are:

0 — Sets a round-robin policy for fault tolerance and load balancing. Transmissions are received and sent out sequentially on each bonded slave interface beginning with the first one available.

1 — Sets an active-backup policy for fault tolerance. Transmissions are received and sent out via the first available bonded slave interface. Another bonded slave interface is only used if the active bonded slave interface fails.

2 — Sets an XOR (exclusive-or) policy for fault tolerance and load balancing. Using this method, the interface matches up the incoming request's MAC address with the MAC address for one of the slave NICs. Once this link is established, transmissions are sent out sequentially beginning with the first available interface.

3 — Sets a broadcast policy for fault tolerance. All transmissions are sent on all slave interfaces.

4 — Sets an IEEE 802.3ad dynamic link aggregation policy. Creates aggregation groups that share the same speed and duplex settings. Transmits and receives on all slaves in the active aggregator. Requires a switch that is 802.3ad compliant.

5 — Sets a Transmit Load Balancing (TLB) policy for fault tolerance and load balancing. The outgoing traffic is distributed according to the current load on each slave interface. Incoming traffic is received by the current slave. If the receiving slave fails, another slave takes over the MAC address of the failed slave.

6 — Sets an Active Load Balancing (ALB) policy for fault tolerance and load balancing. Includes transmit and receive load balancing for IPV4 traffic. Receive load balancing is achieved through ARP negotiation.