Step 2 - View MAC Table using brctl showmacs command In the output, each row represents MAC address learnt at each port of the Linux bridge. The important columns in the output are ‘is local?’, ‘port no’ and ‘mac addr’. Step 2: Next execute the command brctl showmacs with the bridge you identified in Step 1 to view the MAC table. Step 1 - Identify the bridge for a given interface Step 1: If you have detected that eth0 interface is having a problem, then using brctl show command you can list all the bridges and identify the Linux bridge bound to eth0. Interpreting MAC Table - Step-by-Step guide Since multiple Linux bridges may be present, one of the best ways to find out the affected VMs for a given physical network port, is by looking at the MAC table of the Linux bridge that is bound to the failed network port. Now if there was a problem with one of the network ports on a server, it will be good to know which VMs are impacted by it. It follows that these VMs will share the resources on that server including the network ports. Let us consider a scenario where Linux bridge is used for virtual networking (as Mechanism driver in OpenStack).

In cloud platforms like OpenStack, virtual machines (VMs) started by different tenants may get scheduled on the same hardware server. And looking at the MAC table learnt by Linux bridges can provide useful insight into the flow of packets. Linux bridges are no different from their hardware counterparts.

MAC Table - Backgroundīridges and Switches forward packets by examining and learning MAC address from incoming packets. In this installment of WILT (What I Learnt Today) series, I will share how MAC Table can be used for troubleshooting Linux bridges. Recently as part of a comment on my blog, I learnt how to view and interpret the MAC table of Linux bridge. In an earlier blog, I have talked about Linux bridge based virtual networking.

How to get the mac add on a linux