Table of Contents

Overview

The following Howto describes how to bond two or more network interfaces into on bonded interface. This is known as IEEE 802.1AX-2008 or under the working group title of 802.3ad.

Preparation

Install the required software packages. 

yum install bridge-utils

Example Configuration

Here is an example on how to create a bonded interface with eth1 and eth2 network cards.

Drivers

First, it is necessary to add the underlying drivers on bonded interfaces. In /etc/modprobe.conf, add the following: 

alias bond0 bonding

Network Configuration

First, you need to manually create or edit the configuration files as follows.

You can leave the HWADDR line alone in the ifcfg-eth* files

/etc/sysconfig/network-scripts/ifcfg-eth1: 

DEVICE=eth1
MASTER=bond0
SLAVE=yes
ONBOOT=yes

/etc/sysconfig/network-scripts/ifcfg-eth2: 

DEVICE=eth2
MASTER=bond0
SLAVE=yes
ONBOOT=yes

/etc/sysconfig/network-scripts/ifcfg-bond0: 

DEVICE=bond0
BOOTPROTO=none
IPADDR=192.168.2.211
NETMASK=255.255.255.0
GATEWAY=192.168.2.1
ONBOOT=yes
BONDING_OPTS="mode=5 miimon=80"

An alternate set of options that has worked well in testing, and is compliant with 802.3ad is: options bonding max_bonds=2 mode=4 miimon=100 downdelay=100 updelay=100 lacp_rate=1 xmit_hash_policy=layer3+4 use_carrier=1

You can find more information on bonding modes and parameters by following the link below.

Firewall Configuration

The firewall needs know about your new bond0 network interface. In the /etc/firewall configuration file, update the LANIF parameter. 

LANIF="bond0"

-or- 

EXTIF="eth0 bond0"
LANIF="eth1 bond1"

Various software packages need to know about this network change. The easiest way to notify these packages about the change is to run: 

service syswatch restart

Notes on Configuration and Performance

Whether you use mode 4 or 5 will largely depend on whether your switch supports 802.3ad. For this to work properly using mode 4, your switch must also support bonding and have its interfaces configured for the bond. Your switch will not automatically detect NIC bonding.

To understand the performance of NIC bonding, you must also understand that the network devices involved are discrete interfaces. This means that network sessions are NOT duplexed over the multiple interfaces and then put back together. Rather, the individual transfer sessions will be conducted over only one interface at a time. This means that if your transactions are all serial, 'network bonding' will not provide any increase in performance. For configurations where multiple sessions are simultaneously performed, these discrete sessions will be farmed out to one network interface or another based on load and capacity.

Also, it is important to note that only the primary interface of the network bond will approach 100% performance capacity under 802.3ad. All secondary interfaces in the bond will produce about 50% of their maximal performance. For example, in a configuration with three 1 Gigabit Ethernet NICs, they will give the same performance as a single '2 gigabit' NIC. (1 x 1 Gb, 2 x .5 Gb)

Links