Linux Bridge Command Examples
April 14, 2022•292 words
The 'brctl' utility from the bridge-utils package has been deprecated for some time, in favour of the 'bridge' command that comes as part of iproute2.
How to use the commands to get information on Linux bridges is not as clear, so I'm jotting down some quick one liners, mostly to help me remember.
NOTE: The '-br' on the 'ip' commands is for 'brief' output, they can be run without this to show more verbose information. You can use '-br' with all 'ip' commands, it's nothing to do with bridges.
Show bridges configured on the system
ip -br link show type bridge
me@server:~$ ip -br link show type bridge
private UP 4c:d9:8f:6d:a9:70 <BROADCAST,MULTICAST,UP,LOWER_UP>
public UP 4c:d9:8f:6d:a9:70 <BROADCAST,MULTICAST,UP,LOWER_UP>
Show interfaces that are part of a given bridge
ip -br link show master <bridge_name>
me@server:~$ ip -br link show master private
eno1 UP 4c:d9:8f:6d:a9:70 <BROADCAST,MULTICAST,UP,LOWER_UP>
tap0 UNKNOWN fe:d9:bb:17:47:9c <BROADCAST,MULTICAST,UP,LOWER_UP>
tap2 UNKNOWN fe:b0:9b:fb:5e:e3 <BROADCAST,MULTICAST,UP,LOWER_UP>
tap1 UNKNOWN fe:11:ca:71:89:1e <BROADCAST,MULTICAST,UP,LOWER_UP>
Display MAC address / forwarding table for a given bridge
bridge fdb show br <bridge_name>
me@server:~$ sudo bridge fdb show br private
4c:d9:8f:af:4d:03 dev eno1 master private
b0:26:28:dc:10:70 dev eno1 master private
33:33:ff:48:00:51 dev private self permanent
33:33:ff:6d:a9:70 dev private self permanent
aa:00:00:21:66:df dev tap0 master private
fe:d9:bb:17:47:9c dev tap0 vlan 1 master private permanent
fe:d9:bb:17:47:9c dev tap0 master private permanent
33:33:00:00:00:01 dev tap0 self permanent
01:00:5e:00:00:01 dev tap0 self permanent
Display MAC addresses learnt on a given bridge port
bridge fdb show br <bridge_name> dev <member_interface>
me@server:~$ sudo bridge fdb show br private dev tap1
aa:00:00:85:fe:67 master private
fe:11:ca:71:89:1e vlan 1 master private permanent
fe:11:ca:71:89:1e master private permanent
33:33:00:00:00:01 self permanent
01:00:5e:00:00:01 self permanent
33:33:ff:71:89:1e self permanent
01:80:c2:00:00:0e self permanent
01:80:c2:00:00:03 self permanent
01:80:c2:00:00:00 self permanent