NIC(Network Interface Card) bonding is also known as Network bonding. It can be defined as the aggregation or combination of multiple NIC  into a single bond interface. It’s main purpose is to provide high availability and redundancy.

In this article we will learn how to configure nic or netwok bonding in CentOS 7 & RHEL 7. In my case i have two interface cards (enp0s3 & enp0s8) and will form a bond interface (bond0).

Prerequisite :

If bonding module is not loaded on your linux box then use the below command to load.

[[email protected] ~]# modprobe bonding

To list the bonding module info, use following command.

[[email protected] ~]# modinfo bonding

Output will be something like below

modinfo-bonding

Step:1 Create Bond Interface File

Create a bond interface file (ifcfg-bond0) under the folder “/etc/sysconfig/network-scripts/

[[email protected] network-scripts]# vi ifcfg-bond0
DEVICE=bond0
TYPE=Bond
NAME=bond0
BONDING_MASTER=yes
BOOTPROTO=none
ONBOOT=yes
IPADDR=192.168.1.70
NETMASK=255.255.255.0
GATEWAY=192.168.1.1
BONDING_OPTS="mode=5 miimon=100"

Save & exit the file.

Specify the IP address, Netmask & bonding modes as per your requirement. In my example i am using ‘mode=5? which is used to provide fault tolerance and load balancing.

Please refer this for Different Modes in NIC bonding

Step:2 Edit the NIC interface files

For ifcfg-enp0s3

[[email protected] ~]# vi /etc/sysconfig/network-scripts/ifcfg-enp0s3
TYPE=Ethernet
BOOTPROTO=none
DEVICE=enp0s3
ONBOOT=yes
HWADDR="08:00:27:69:60:c9"
MASTER=bond0
SLAVE=yes

For ifcfg-enp0s8

[[email protected] ~]# cat /etc/sysconfig/network-scripts/ifcfg-enp0s8
TYPE=Ethernet
BOOTPROTO=none
DEVICE=enp0s8
ONBOOT=yes
HWADDR="08:00:27:ea:71:8d"
MASTER=bond0
SLAVE=yes
Step:3 Restart the Network Service

Below command will restart the network service and will bring above changes into the effect.

[[email protected] ~]# systemctl restart network.service
Step:4 Test & Verify bond interface.

Use ‘ifconfig‘ & ‘ip add‘ command to check bond interface along with its slave interfaces.

ifconfig-bond

Use following command to view bond interface settings like bonding mode & slave interface.

[[email protected] ~]# cat /proc/net/bonding/bond0

bonding-settings

Step:5 Fault tolerance testing

To test the fault tolerance we can down one interface and check whether you are still able access the server.

[[email protected] ~]# ifdown enp0s8
Device 'enp0s8' successfully disconnected.
[[email protected] ~]#

fault-tolerance-bonding