[c-nsp] Strange problem w/ 3560 and Linksys Switch

[Aaron Riemer]

Hi there, 

Have you checked the arp table on switch b to see if the mac's already exist
for the addresses you are attempting to ping? I had a similar problem and I
believe it was related to either a stale arp cache or the switch stored in
its mac table the mac addresses behind an uplink port that was since blocked
by spanning-tree. This would explain why you are not seeing arp requests. Do
a 'debug arp' on switch B and see what you get.

Let us know how you go. 

Cheers,

Aaron.

-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Garry
Sent: Thursday, 23 August 2007 7:27 PM
To: cisco-nsp at puck.nether.net
Subject: [c-nsp] Strange problem w/ 3560 and Linksys Switch

I've come across a strange problem at a customer site ... maybe somebody 
has an idea ... I'm more or less out of them ...

OK, base setup is a ring of three switches, two are 3560G, one is a 
Linksys SRW2024. The Ciscos are connected via a GigE Port channel w/ 2 
copper links, the Linksys is connected to one fiber port on each 3560. 
Spanning tree is working fine, one Cisco has set its connection to block 
(referenced as switch "B")

What seems to happen is that I can't get any broadcast/multicast packets 
through the active Cisco switch ... when I do a ping to any device 
connected to the Linksys from switch A, everything is fine. Doing the 
same from Switch B fails, unless it can first learn the MAC address by 
seeing a packet from that device.

I've done a tcpdump on a linux box hooked up to the linksys, I do not 
see any ARP requests generated by Switch B.

What could be causing this? The fiber links are configured as trunk 
ports on both Ciscos, and the appropriate VLANs are assigned on the 
Linksys side. I've also set the Linksys fiber ports to "multiple hosts", 
though the checking shouldn't even be on to begin with ...

Anybody have an idea what could be causing this behavior?

Thanks!!!

-gg
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