mac address of edge switches is not shown in upstream switch mac table

[rsie2019]

HI,

I have switches connected like below

sw1(fa0/0) ----sw2(fa0/1)-- Host1

Can i expect the sw2 mac address to be listed in 'show mac address-table' command on sw1 and vice versa.

I could see the Host1 mac address in sw2 and sw,1 but sw2 mac address is not shown in mac address table, is this expected behaviour.

Please clarify

Thanks,

Hari

[Joseph W. Doherty]

Depends on frame traffic flows and MAC table time out settings.

A switch will record, for some amount of time, any ingress frame's source MAC.

For example, if host on switch 2 ARPs for another host, also on switch 2, both switches may have host MACs in their MAC tables.  Then, those two hosts send much unicast traffic across switch 2.  That will keep their MACs known on switch 2, but on switch 1 they age out.

[rsie2019]

Thanks Joseph.

That is correct but i want to know if we can expect switch2 mac address in switch1 bridge table.Is there any scenarios where that mac population can happen.

When a switch  generates frames like for stp/vtp/lacp,will the  mac address table get populated due to that?

I configured layer 2 port-channel in nexus devices but still i don't see the mac address of the neighbour switch.Is this expected behaviour.

In general, can we expect neighbour switch mac address in bridge tables.

[MHM Cisco World · Accepted solution]

You correct' stp and other l2 protocol use SW mac as source but the SW receive it not add source mac to mac table' but why?

Because when SW exchange l2 protocol frame the traffic always p2mp i.e. from one SW to all other SW (multicast) so no need to keep source mac since there is no p2p.

The only case you see not sw mac but mac of vlan of sw is when this vlan use for ping/telnet/ssh ....etc management traffic.

[STD_NetWorld]

@rsie2019 Yes, it's expected behaviour, switch MAC address are not showing on "show mac address table". on mac address table you can see only end device mac address and SVI mac address.

Switch mac add are using for backend switch management purpose like spanning tree and many more.

[rsie2019]

Thank you folks for the explanations