Adding bonding interface to CentOS 8 – editing configuration files only

This article shows what files to add if you want to add a bonding interface under CentOS 8 without invoking the Network manager command utility.
Our goal is to use one boding group with the name bond0 in LACP (aka 802.3ad) mode (but it could be any of the other types) with two networks 10Gbps interfaces. The setup resented here uses NetworkManager, which handles the loading of bonding module properly.

In fact, the network-scripts are now deprecated and they are missing from the system (but they still exist in the additional package – “network-scripts”, who knows till when? do not rely on them!).

The configuration files are with the same syntax as under CentOS 7, but this time the network manager parses them. The ifup and ifdown still exist and they just call the Network manager when executed (unless the “network-scripts” package is installed). If you need to enable bonding without any configuration files (for emergency situations) you may still use – How to enable Linux bonding without ifenslave

What do you need:

  • Ensure you have installed: “iputils” and “NetworkManager” packages
    dnf install -y NetworkManager iputils
  • Ensure the NetworkManager service is running
    systemctl enable NetworkManager
    systemctl start NetworkManager

STEP 1) Configure the bonding device

The boding interface’s name will be bond0 and the configuration will be located in /etc/sysconfig/network-scripts/ifcfg-bond0

BONDING_OPTS="mode=4 miimon=100"

As you can see we use IPADDR0, PREFIX0 and GATEWAY0, because it is easy to add multiple IPs (and gateways) with suffix 1,2,…N (just add IPADDR1,PREFIX1 and if any GATEWAY1). Add the default gateway for the system in /etc/sysconfig/network


STEP 2) Configuring the network cards

Using two network cards in our bodning group we have two configuration files for each of the network interaces:
The configuration file for the first network interface ens1f0 (in your case may be with another name) is /etc/sysconfig/network-scripts/ifcfg-ens1f0:


And only change the name of the second network card in the configuration file with name /etc/sysconfig/network-scripts/ifcfg-ens1f1:


Of course, the UUID file should be different in all configuration files (aka devices).

STEP 3) Start the bonding network interface

Start the inteface with ifup

[root@srv ~]# ifup bond0
Connection successfully activated (master waiting for slaves) (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/4)

No error and output for successful activation – now your machine may use the bond0 network interface.
The above command will start only the bonding interface, but you may want to restart the whole network:

systemctl restart NetworkManager

Or only reloading the NetworkManager configurations

nmcli connection reload

And the boding is UP and RUNNING:

[root@srv ~]# ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether ac:1f:6b:00:77:6e brd ff:ff:ff:ff:ff:ff
3: eno2: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN group default qlen 1000
    link/ether ac:1f:6b:00:77:6f brd ff:ff:ff:ff:ff:ff
4: ens1f0: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc mq master bond0 state UP group default qlen 1000
    link/ether 00:1b:21:cc:32:ef brd ff:ff:ff:ff:ff:ff
5: ens1f1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc mq master bond0 state UP group default qlen 1000
    link/ether 00:1b:21:cc:32:ef brd ff:ff:ff:ff:ff:ff
6: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
    link/ether 00:1b:21:cc:32:ef brd ff:ff:ff:ff:ff:ff
    inet brd scope global noprefixroute bond0
       valid_lft forever preferred_lft forever


If you receive error of the kind even the /etc/sysconfig/network-scripts/ifcfg-bond0 exists

[root@srv ~]# ifup bond0
Error: unknown connection '/etc/sysconfig/network-scripts/ifcfg-bond0'

Just remove (comment out) the line “NM_CONTROLLED=no”. The Network manager should control the interface because the Network manager parses the configuration files unless you have not installed the deprecated network scripts – network-scripts package (which is not installed and used by default and it is unknown how long will be supported).

One thought on “Adding bonding interface to CentOS 8 – editing configuration files only”

  1. This gave me the most direct and perfect steps for Network bonding. Thanks for the knowledge share. I did face the error “Error: unknown connection ‘/etc/sysconfig/network-scripts/ifcfg-bond0′” and i found the perfect solution here.

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