Adding new Bridge in CentOS Linux KVM

We have 4 ethernet network ports running on a server. Recently we have activated another ports with an upstream provider, we decided to active one of the port to create the VM on the new upstream provider’s port.

First, check how many bridge network is running on your server

# brctl show 
bridge name     bridge id               STP enabled     interfaces
br0             8000.00219b9db5e5       no              eth1
                                                        vnet0
                                                        vnet1
                                                        vnet2
                                                        vnet3
                                                        vnet4
virbr0          8000.5254001bf78c       yes             virbr0-nic

From the above result, it shows currently there is one bridge network on eth1. The VMs are running on bridge 1. To add new bridge network, execute the command below;

# brctl addbr br1

Congrats, the bridge interface has been create, next is to configure the network interface script at system side. Go to /etc/sysconfig/network-scripts/, next create a new file name vi ifcfg-eth2 with the configuration below;

DEVICE="eth2"
HWADDR="78:2B:CB:20:8E:F8"
NM_CONTROLLED="yes"
ONBOOT="yes"
BRIDGE="br1"

Above config is to create a bridge between eth2 with br1. Next create the configuration file for br1 at /etc/sysconfig/network-scripts/, vi ifcfg-br1

DEVICE="br1"
BOOTPROTO="none"
ONBOOT="yes"
TYPE="Bridge"

Please take note that we have the host server configured with IP Address on eth0, that is the reason why we don’t configure IP Address on br1.

That is done with network interface configuration, next restart the network services. Please take note that if you are ssh-ing into the server, you might experience disconnection for 10-15 seconds. Before restarting the network service, make sure the config is correct, we do not responsible if your server completely went down 😉

# /etc/init.d/network restart

If you connectivity came up and alive, congrats the network interface configuration has completed. Next add the network interface into bridge network

# brctl addif br1 eth2

Now you will see new interface has been added with brctl show

# brctl show 

bridge name     bridge id               STP enabled     interfaces
br0             8000.00219b9db5e5       no              eth1
                                                        vnet0
                                                        vnet1
                                                        vnet2
                                                        vnet3
                                                        vnet4
br1             8000.00219b9db5e3       no              eth2
virbr0          8000.5254001bf78c       yes             virbr0-nic