CentOS 8.x Creating bridge interfaces (br0) for virtual hosts to use shared interface

Home > CentOS > CentOS 8.x > System Administration > Network configuration > CentOS 8.x Creating bridge interfaces (br0) for virtual hosts to use shared interface

To create bridge interfaces in CentOS 8.0 (or even 7.0) almost same settings as described in older Creating bridge interfaces (br0) for virtual hosts to use shared interface, with an additional 'NAME=' parameter in both interface configuration files. Example configuration files for CentOS 8.0 bridge are:

In /etc/sysconfig/network-scripts/ifcfg-br0

   NAME="br0"
   DEVICE="br0"
   TYPE="Bridge"
   BOOTPROTO="dhcp"
   ONBOOT="yes"

In /etc/sysconfig/network-scripts/ifcfg-<interface-name>

   NAME="<interface-name>"
   DEVICE="<interface-name>"
   TYPE="Ethernet"
   BOOTPROTO="none"
   ONBOOT="yes"
   BRIDGE="br0"

where <interface-name> can be eth0, enp0s1, eno1, etc.

If you want to specify additional settings such as for IPV6 they should all go in ifcfg-br0 file only. Example settings that can go to ifcfg-br0 are:

DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy

These should be removed from ifcfg-<interface-name> file to avoid duplication.

Caution: You will get disconnected if you run below commands remotely. Plan for secondary access to machine via virtualization platform / iDRAC etc. before doing below.

For changes to take effect restart NetworkManager service using:

systemctl stop NetworkManager;   systemctl start NetworkManager

OR stop / start networking using:

nmcli networking off; nmcli networking on

Validate that bridge is having ip address and not interface:

nmcli connection show
nmcli connection show <ethernet-interface> | grep br0

Should show

connection.master: br0

Other option is to use command:

bridge link

which should show all interfaces and their master bridges. Example output of above command is:

2: ens192: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 master br0 state forwarding priority 32 cost 100 
5: virbr0-nic: <BROADCAST,MULTICAST> mtu 1500 master virbr0 state disabled priority 32 cost 100

Disabling bridge on laptop to use wifi

If we create bridge using above steps, it might be required to disable it on laptop so that wifi can be used. Without changing config files or restarting network services use following to disable bridge on laptop and switch network to wifi:

1. Ensure that both ifcfg-br0 and ifcg-<interface-name> files have

   NM_CONTROLLED=yes

2. Then we can shutdown bridge if required using:

   nmcli connection down br0

3. After this use ping to test if traffic is now getting routed via wireless as desired or not.

Older information on this can be found at:

• Creating bridge interfaces (br0) for virtual hosts to use shared interface

Refer:

• https://computingforgeeks.com/how-to-create-a-linux-network-bridge-on-rhel-centos-8/

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