Network bonding is where you take two or more network interfaces and you combine them into a single logical network interface. This can be great for one of two reasons: one is to create higher bandwidth and throughput, and the other is for fault tolerance and high availability.

One great thing about network bonding is that if one interface goes down or is unplugged, another network interface in the bond will pick up the slack and it will continue working. So Linux uses a special kernel module named bonding, and it includes seven different modes that can be used. However, most use cases can be covered with two or three of these.

Next, I'm going to show you how to set up a network bond on CentOS. This is a very simple and straightforward process. To begin, just type “nmtui” into the terminal to enter the network text user interface. From here, select “Edit a connection”, and select “Add”. You will want to select “Bond” and then select “Create”. Once inside the editor connection tab, under “Device”, type “bond0”, or whatever you want your bond to be named and then move down to “Add”, and begin adding the network interfaces you want to be part of the bond. Enter the name of the interfaces you want to use under the “Device” section.

One note when choosing Ethernet ports, EN01 and EN02 are your motherboard’s onboard Ethernet ports, so you may want to stay away from using this for your bond if you have NIC cards installed. You can also configure the type of bond in here, or leave it to the default round-robin configuration. Here at 45 Drives, we use active backup or 802.3AD mode, which can also be called LACP mode.

Once you finish adding interfaces to your bond in the ipv4 config section, you can either leave it as it is, or allow DHCP to assign an IP to your newly created bond, or edit this to assign it to a static IP, which is recommended. If you choose to use a static IP however, be sure to use an address outside of your DHCP server’s range to avoid clashes. You can get this information from your local network admin.

Finally, back out to the “Activate a Connection” screen, scroll down to your new bond0 interfaces, and select “Deactivate”, and then reactivate when it finishes. Once this completes, you're now ready to test, so exit your nmtui. One thing to note, the activation of the bond may take a little while to complete. Once back in the terminal, type “ip addr show bond0” to bring up the addresses for your new bond, or just “ip a” to pull up all network interfaces.

One thing to note about mode 1 active backup is it’s just like it sounds. It provides no extra bandwidth, but it does provide fault tolerance. One great benefit about this-it's the easiest one to set up. And now for mode 4 or LACP; it provides load balancing for extra bandwidth as well as fault tolerance, however, your switch must support this.

So, if you want to find out more, such as detailed guides on how to do everything talked about in this video, be sure to check out our knowledge base articles; every link will be down below. So thanks for tuning in guys, hopefully this video was helpful to some of you out there, and be sure to check back next week for another tech video.