4.4. Using the Command Line Interface (CLI)

A bond is created using the bonding kernel module and a special network interface called a channel bonding interface.

4.4.1. Check if Bonding Kernel Module is Installed

In Red Hat Enterprise Linux 7, the bonding module is not loaded by default. You can load the module by issuing the following command as root: 
~]# modprobe --first-time bonding
This activation will not persist across system restarts. See the Red Hat Enterprise Linux System Administrator's Guide for an explanation of persistent module loading. Note that given a correct configuration file using the BONDING_OPTS directive, the bonding module will be loaded as required and therefore does not need to be loaded separately.
To display information about the module, issue the following command: 
~]$ modinfo bonding
See the modprobe(8) man page for more command options.

4.4.2. Create a Channel Bonding Interface

To create a channel bonding interface, create a file in the /etc/sysconfig/network-scripts/ directory called ifcfg-bondN, replacing N with the number for the interface, such as 0.
The contents of the file can be based on a configuration file for whatever type of interface is getting bonded, such as an Ethernet interface. The essential differences are that the DEVICE directive is bondN, replacing N with the number for the interface, and TYPE=Bond. In addition, set BONDING_MASTER=yes.

Example 4.1. Example ifcfg-bond0 Interface Configuration File

An example of a channel bonding interface. 
DEVICE=bond0
NAME=bond0
TYPE=Bond
BONDING_MASTER=yes
IPADDR=192.168.1.1
PREFIX=24
ONBOOT=yes
BOOTPROTO=none
BONDING_OPTS="bonding parameters separated by spaces"
The NAME directive is useful for naming the connection profile in NetworkManager. ONBOOT says whether the profile should be started when booting (or more generally, when auto-connecting a device).

Important

Parameters for the bonding kernel module must be specified as a space-separated list in the BONDING_OPTS="bonding parameters" directive in the ifcfg-bondN interface file. Do not specify options for the bonding device in /etc/modprobe.d/bonding.conf, or in the deprecated /etc/modprobe.conf file.
The max_bonds parameter is not interface specific and should not be set when using ifcfg-bondN files with the BONDING_OPTS directive as this directive will cause the network scripts to create the bond interfaces as required.
For further instructions and advice on configuring the bonding module and to view the list of bonding parameters, see Section 4.5, “Using Channel Bonding”.

4.4.3. Creating SLAVE Interfaces

The channel bonding interface is the “master” and the interfaces to be bonded are referred to as the “slaves”. After the channel bonding interface is created, the network interfaces to be bound together must be configured by adding the MASTER and SLAVE directives to the configuration files of the slaves. The configuration files for each of the slave interfaces can be nearly identical.

Example 4.2. Example Slave Interface Configuration File

For example, if two Ethernet interfaces are being channel bonded, eth0 and eth1, they can both look like the following example: 
DEVICE=ethN
NAME=bond0-slave
TYPE=Ethernet
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes
In this example, replace N with the numerical value for the interface. Note that if more than one profile or configuration file exists with ONBOOT=yes for an interface, they may race with each other and a plain TYPE=Ethernet profile may be activated instead of a bond slave.

4.4.4. Activating a Channel Bond

To activate a bond, open all the slaves. As root, issue the following commands: 
~]# ifup ifcfg-eth0
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/7)
~]# ifup ifcfg-eth1
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/8)
Note that if editing interface files for interfaces which are currently “up”, set them down first as follows: 
ifdown ethN
Then when complete, open all the slaves, which will open the bond (provided it was not set “down”).
To make NetworkManager aware of the changes, issue a command for every changed interface as root: 
~]# nmcli con load /etc/sysconfig/network-scripts/ifcfg-device
Alternatively, to reload all interfaces: 
~]# nmcli con reload
The default behavior is for NetworkManager not to be aware of the changes and to continue using the old configuration data. This is set by the monitor-connection-files option in the NetworkManager.conf file. See the NetworkManager.conf(5) manual page for more information.
To view the status of the bond interface, issue the following command: 
~]# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT qlen 1000
    link/ether 52:54:00:e9:ce:d2 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT qlen 1000
    link/ether 52:54:00:38:a6:4c brd ff:ff:ff:ff:ff:ff
4: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT
    link/ether 52:54:00:38:a6:4c brd ff:ff:ff:ff:ff:ff

4.4.5. Creating Multiple Bonds

In Red Hat Enterprise Linux, for each bond a channel bonding interface is created including the BONDING_OPTS directive. This configuration method is used so that multiple bonding devices can have different configurations. To create multiple channel bonding interfaces, proceed as follows:
  • Create multiple ifcfg-bondN files with the BONDING_OPTS directive; this directive will cause the network scripts to create the bond interfaces as required.
  • Create, or edit existing, interface configuration files to be bonded and include the SLAVE directive.
  • Assign the interfaces to be bonded, the slave interfaces, to the channel bonding interfaces by means of the MASTER directive.

Example 4.3. Example multiple ifcfg-bondN interface configuration files

The following is an example of a channel bonding interface configuration file: 
DEVICE=bondN
NAME=bondN
TYPE=Bond
BONDING_MASTER=yes
IPADDR=192.168.1.1
PREFIX=24
ONBOOT=yes
BOOTPROTO=none
BONDING_OPTS="bonding parameters separated by spaces"
In this example, replace N with the number for the bond interface. For example, to create two bonds create two configuration files, ifcfg-bond0 and ifcfg-bond1, with appropriate IP addresses.
Create the interfaces to be bonded as per Example 4.2, “Example Slave Interface Configuration File” and assign them to the bond interfaces as required using the MASTER=bondN directive. For example, continuing on from the example above, if two interfaces per bond are required, then for two bonds create four interface configuration files and assign the first two using MASTER=bond0 and the next two using MASTER=bond1.