Re: Learning MAC Addresses

iaglindro · ‎06-20-2003

I have a problem concerning a 3550-24 switch learning MAC addresses. I'm on the process of performing failover tests for a client and encountered this problem.

Below is the topology:

PIX(active) ---> 3550-24-A ---> 2621-A router

PIX(standby) ---> 3550-24-B --->2621-B router

3550-24-A ---> 3550-24-B (via cross cable)

when 3550-24-A is powered off (to simulate a defective unit), standby PIX becomes active. when 3550-24-A is powered on, a laptop connected to 3550-24-A cannot ping PIX (standby) and 2621-B but when transferred to 3550-B, can ping PIX (standby) and 2621-A but cannot ping PIX (active) and 2621-B. I found out that on 3550-A, the port connecting to 3550-B cannot learn mac-addresses from 3550-B but 3550-B port can learn mac-addresses from 3550-A. Is there a way to force a port on 3550-A to learn mac-addresses?

thanks in advance.

cheers,

-ian

rjackson · ‎06-20-2003

I assume these 3550s are just switching and are not vlan'd. There is no reason 3550a should not learn addresses from packets coming from b unless you configured it so with some port security. Can the laptop see standby and 2621b before the failover starts? It should. Do you understand that the pix's will swap addresses during failover ( active becomes standby and standby becomes active) then your config controls whether they swap back after recovery. In other words during and after failover the standby address is on the pix attached to 3550a. Also, are the 2621s running hsrp?

iaglindro · ‎06-20-2003

I assume these 3550s are just switching and are not vlan'd

---> they are only switching

There is no reason 3550a should not learn addresses from packets coming from b unless you configured it so with some port security.

---> no port security, but still cannot learn mac-address from other switch. what should i do to speed up learning of the mac? its been hours but still it cannot learn the mac through the cross cable port till i reload the switch. shut/no shut does nothing to contribute to resolution of problem.

Can the laptop see standby and 2621b before the failover starts? It should.

---> Yes it does.

Do you understand that the pix's will swap addresses during failover ( active becomes standby and standby becomes active) then your config controls whether they swap back after recovery. In other words during and after failover the standby address is on the pix attached to 3550a.

---> i understand that. but problem is on link between switches (again link does not learn the mac addresses).

Also, are the 2621s running hsrp? Yes they are. but i'm trying to ping the individual router ip address after the 3550a powers on.

hope this helps in visualizing my problem. again thanks for your time.

cheers,

-ian

rjackson · ‎06-20-2003

try pinging the laptop from the pix and router. (verify it is not in their arp tables first.) they should broadcast arps and swb should flood it out the port to swa. If swa doesnt learn the addresses from that something is broken.

iaglindro · ‎06-23-2003

I already found solution. Port fast on every switchport. thanks for your time. help very much appreciated

cheers,

-ian

rmv72 · ‎06-23-2003

but how the port fast could be the reason of problem?

rjackson · ‎06-23-2003

Although it is safe if you network is built without loops it is never recommended to enable portfast on ports that link two switches.

iaglindro · ‎06-23-2003

Yes its true that its not recommended because of loop issues but my setup only has two switches anyway. Actually, everytime you enable it on the port, there's always a caution.