[c-nsp] 2970 turns into a hub for a few moments

[Church, Chuck]

Unknown destination mac?

--- Original Message ---
From:"Vincent De Keyzer" <vincent at dekeyzer.net>
Sent:Wed 12/27/06  10:13 am
To:"cisco-nsp at puck.nether.net" <cisco-nsp at puck.nether.net>
Cc:
Subj:[c-nsp] 2970 turns into a hub for a few moments

Hello,

 

a few days ago, some people on the office network started to complain about
application timeouts/cuts (a few times a day). Since different people were
complaining about different applications, the network seemed the right place
to look at.

 

We have placed several laptops in several points of the network, running a
sensible application plus Ethereal. What we saw was very weird: from time to
time (and it coincides with the applications timeouts), the switches starts
forwarding to the laptop ports traffic that is neither broadcast, nor
unicast for the laptops. Just like if the switch would become a hub from
time to time. It lasts for "a few seconds" (we still need to narrow this
down), then it starts behaving normally again. We believe that this produces
some temporary congestion on the network, which causes the applications
problems.

 

Does anyone have an idea on what could be causing this?

 

Vincent

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