Hi Matt,

We took out our Lucent-based APs as part of the project but that's a
little scary.  So I can't comment on the exact behavior of that AP.

When you say that it drops its IP, do you mean that the IP address on
the client changes to invalid/169.254 ?

If that is the case, I would check to see if the drop is at the DHCP
mid-point pf the lease when most clients perform a renew.  Unless you
have DHCP server filtering on your APs, it's trivial to put up a fast
rogue DHCP server that might cause havoc.

Can you easily reproduce the problem?

... Jonn Martell, wireless.ubc.ca

Matt Ashfield (UNB) wrote:

Hi All,

I've been fighting a problem on campus where students laptops appear to be
dropping their ip connection to the network sporadically. I'm hoping someone
can shed some light on the situation.
I think I've narrowed it down to the broadcast limiting in the Access
Points. I was using the default threshold settings, and thinking I either
need to dramatically up them or remove them altogether. The definition in
the Avaya "documentation" (<insert your own joke here>) states:
"If the maximum value of Broadcast or Multicast per second is exceeded, the
Base Station will ignore all subsequent messages issued by the particular
network device, or ignore all messages of that type."
The default settings limit to 30 frames/sec for an address and 60 for a port
(ethernet and wireless). So what I take this to mean is, if a mac address
transmits more than 30 broadcasts/second (in our network, not unheard of),
then it gets ignored. Now, this would seem to be what his happening. Except
the problem is, the address getting blocked/ignored is the router address
(caused by an arp storm perhaps).
So my question is, once an address is ignored, what does it take to get the
access point to allow that address to be heard again? Is there a time limit?
How does this work exactly?
Any info/insight would be greatly appreciated.

Thanks

Matthew Ashfield
Network Analyst
Integrated Technology Services
University of New Brunswick
(506) 447-3033

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