There are many situations in which someone would like to configure network bonding or channel bonding on a server… In most cases it is done for the network card redundancy. You can bond two network cards together in an “active/backup” configuration and in case one of your network cards fails all of the traffic will be instantly switched to the other, still working network card.

You can also bond two network cards together to get more network traffic throughput. This means that you need to configure your network bonding in “load-balancing” mode and make both network cards active at the same time. This way you double the network throughput to and from your server. But if you want to succesfully run a “load-balancing” bonding configuration your networking infrastructure (routers, switches,…) MUST ALSO be configured for port load balancing.

Read more about the problems you might come to HERE.

Let’s start our Configure Network Bonding on CentOS guide!

1. Create bonding configuration file

Create a new file called bonding.conf in /etc/modprobe.d directory (full path – /etc/modprobe.d/bonfing.conf) and insert the following lines.

• Active backup configuration (one active network card)

alias bond0 bonding
options bond0 miimon=80 mode=1

• Balance-tlb configuration

alias bond0 bonding
options bond0 miimon=80 mode=1

2. Create new network interface

Create bond0 configuration file (full path – /etc/sysconfig/network-scripts/ifcfg-bond0) and insert the following lines.

DEVICE=bond0
IPADDR=your_ip_address
NETMASK=network_mask
GATEWAY=gateway_address
ONBOOT=yes
BOOTPROTO=none
USERCTL=no

 3. Edit network configuration

Change the contents of exsisting ifcfg-eth0 and ifcfg-eth1 configuration files (full path -/etc/sysconfig/network-scripts/ifcfg-eth0 and /etc/sysconfig/network-scripts/ifcfg-eth1)and insert the following lines.

• /etc/sysconfig/network-scripts/ifcfg-eth0

DEVICE=eth0
ONBOOT=yes
BOOTPROTO=none
USERCTL=no
MASTER=bond0
SLAVE=yes

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

DEVICE=eth1
ONBOOT=yes
BOOTPROTO=none
USERCTL=no
MASTER=bond0
SLAVE=yes

4. Restart network

Restart networking and check the status of bonding.

[root@foo ~]# service network restart
[root@foo ~]# cat /proc/net/bonding/bond0
Ethernet Channel Bonding Driver: v3.6.0 (September 26, 2009)
Bonding Mode: fault-tolerance (active-backup)
Primary Slave: None
Currently Active Slave: eth0
MII Status: up
MII Polling Interval (ms): 80
Up Delay (ms): 0
Down Delay (ms): 0
Slave Interface: eth0
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 08:00:27:6b:06:7e
Slave queue ID: 0
Slave Interface: eth1
MII Status: up
Speed: 1000 Mbps
Duplex: full
Link Failure Count: 0
Permanent HW addr: 08:00:27:57:b2:a9

5. Test bonding

You can test the network bonding by dropping active network card (ifdown eth0) and check that the network connection is still working…