How to Create NIC Teaming or Bonding in CentOS 8 / RHEL 8

NIC teaming is the aggregation or bonding of two or more network links into a single logical link to provide redundancy and high availability. The logical interface/link is known as a team interface. In the event that the active physical link goes down, one of the backup or reserved links automatically kicks and ensures an uninterrupted connection to the server.

Teaming Terminologies

Before we roll our sleeves, it’s crucial to familiarize yourself with the following terminologies:

• Teamd – This is the nic teaming daemon that uses the libteam library to communicate with team devices via the Linux kernel.
• Teamdctl– This is a utility that allows users to control an instance of teamd. You can check and change the port status, as well as switch between backup and active states.
• Runner – These are units of code written in JSON and are used for the implementation of various NIC teaming concepts. Examples of runner modes include Round robbin, load balancing, broadcast, and active backup.

For this guide, we will configure NIC teaming using the active-backup mode. This is where one link remains active while the rest are on standby and reserved as backup links incase the active link goes down.

Without much further ado, let’s begin.

Step 1: Install the teamd Daemon in CentOS

Teamd is the daemon that is responsible for creating a network team that will act as the logical interface during runtime. By default, it comes installed with CentOS/RHEL 8. But if, for whatever reason, it’s not installed, execute the following dnf command to install it.

$ sudo dnf install teamd

Once installed verify that teamd is installed by running the rpm command:

$ rpm -qi teamd

Step 2: Configure NIC Teaming in CentOS

To configure NIC teaming we will use the handy nmcli tool that can be used for the management of NetworkManager service. In my system, I have 2 NIC cards that I’m going to bond or combine to create a logical team interface: enp0s3 and enp0s8. This may be different in your case.

To confirm the active network interfaces run:

$ nmcli device status

The output confirms the existence of 2 active network connections. To gather more information about the interfaces like UUID, run the command:

$ nmcli connection show

To create a network teaming link or interface, which will be our logical link, we are going to delete the existing network interfaces. Thereafter we will create slave interfaces using the deleted interfaces and then associate them with the teaming link.

Using their respective UUID’s execute the commands below to delete the links:

$ nmcli connection delete e3cec54d-e791-4436-8c5f-4a48c134ad29
$ nmcli connection delete dee76b4c-9alb-4f24-a9f0-2c9574747807

This time when you check the interfaces, you’ll notice that they are disconnected and provide no connection to the server. Basically, your server will be isolated from the rest of the network.

$ nmcli device status

Next, we are going to create a team interface called team0 in active-backup runner mode. As earlier stated, the active backup runner mode uses one active interface and reserves the others for redundancy in case the active link goes down.

$ nmcli connection add type team con-name team0 ifname team0 config '{"runner": {"name": "activebackup"}}'

To view the attributes assigned to the team0 interface run the command:

$ nmcli connection show team0

Perfect! At this point, we only have one interface up, which is the team0 interface as shown.

$ nmcli connection show

Next, configure IP address for the team0 interface as shown using the nmcli command. Be sure to assign the IP’s according to your network’s subnet & IP addressing scheme.

$ nmcli con mod team0 ipv4.addresses 192.168.2.100/24
$ nmcli con mod team0 ipv4.gateway 192.168.2.1
$ nmcli con mod team0 ipv4.dns 8.8.8.8
$ nmcli con mod team0 ipv4.method manual
$ nmcli con mod team0 connection.autoconnect yes

Thereafter, create slave links and associate the slaves to the team link:

$ nmcli con add type team-slave con-name team0-slave0 ifname enp0s3 master team0
$ nmcli con add type team-slave con-name team0-slave1 ifname enp0s8 master team0

Check the status of the links again, and you’ll notice that the slave links are now active.

$ nmcli connection show

Next, deactivate and activate the team link. This activates the connection between the slave links and the team link.

$ nmcli connection down team0 && nmcli connection up team0

Next, verify the state of the team link connection as shown.

$ ip addr show dev team0

We can see that the link is up with the correct IP addressing that we configured earlier.

To retrieve additional details about the team link, run the command:

$ sudo teamdctl team0 state

From the output, we can see that both links (enp0s3 and enp0s8) are up and that the active link is enp0s8.

Step 3: Testing Network Teaming Redundancy

To test our active-backup teaming mode, we will disconnect the currently active link – enp0s3 – and check whether the other link kicks in.

$ nmcli device disconnect enp0s3
$ sudo teamdctl team0 state

When you check the status of the teaming interface, you’ll find that the link enp0s8 has kicked in and serving connections to the server. This confirms that our setup is working!

Step 4: Deleting a Network Teaming Interface

If you wish to delete the teaming interface/link and revert to default network settings, first bring down the teaming link:

$ nmcli connection down team0

Next, delete the slaves.

$ nmcli connection delete team0-slave0 team0-slave1

Finally, delete the teaming interface.

$ nmcli connection delete team0

At this point, all the interfaces are down and your server is not reachable. To activate your network interfaces and regain connectivity, run the commands:

$ sudo ifconfig enp0s3 up
$ sudo ifconfig enp0s8 up
$ sudo systemctl restart NetworkManager

Conclusion

NIC teaming offers an excellent solution for network redundancy. With 2 or more network interfaces, you can configure a teaming interface in any runner mode to ensure high availability in the event one link goes down accidentally. We do hope that you found this guide helpful. Hit us up and let us know how your experience was.