problem with switches

[infintry]

For the past few weeks i've been having connectivity problems with our cascading switches.
We have 8 switches (3548's) and one 3508)cascading.
The problem is that during the day the lights start flashing very fast and the entire network pretty much goes down. Users lose connection and everything becomes so slow. Rebooting the 3508 seems to fix the problem temporarily but after a few hours it comes back again. The lights flash very fast on all the switches at the same time
I dont have full access to this equipment but i am trying to get the passwords to see if i can find anything wrong.
Has anyone encountered this problem before and what can i do to fix it. any information will be appreciated thanks

 

[hexn]

First thing I would do is readup on troubleshooting/maximizing spanning-tree as this is generally the problem with cascading this many switches.

 

[infintry]

i think i am narrowing the problem down to a particular switch - i am getting very high collision rates on that switch and sometimes it re-boot itself.

 

[jgercken]

Ahh, your first broadcast storm. *sniff* I remember mine like it was yesterday.

Do you have a sniffer? You can capture and determine the culperit or start unplugging ports on the suspected source switch.

You can also enable port storm-control to tell the switch to detect a storm and drop packets over a predefined threshold.

more at:

http://www.cisco.com/univercd/cc/td/doc/product/lan/c2900xl/29_35wc3/cref/clicmds.htm#55041

Jeff

 

[infintry]

I dont have a sniffer yet but i am getting one this week -
for now i will remove the connections i have on this switch and transfer them to another switch. I will see if that makes any differece
thanks

 

[CHM1]

I had a similar problem last year : no more connectivity after some (but not all) power shutdown (due to switching to electrogen groups) : the switches were behind an UPS but not all.
Finally, after many tries (spanning tree, ...) (and many monthes), a modification on the grounding of the electrical installation brought the solution to the problem.
I have no reasonable explanation but now it works fine.

 

[infintry]

You know what i think i will definitely take a look at the factor also. All my switches and routers are behind UPS and these UPS are full. It wont hurt to distribute the load to other ones. I think i will get some extra ups just in case.
THANKS.