Packet activity light always amber 2

[glen812]

Hey everyone, got a question.
I've been working in my current environment for some time and have not seen this before. We have between 25 and 30 3Com 3300(12 and 24 port),4400, 4900 and all have been working well for some time. What I'm looking at now is for the most part, all these 3coms have the packet light always on (they used to blink with activity). I've used 3Com Trancend, 3Com Net Supervisor, and NetMon within NT to find what's doing this. As far as connectivity goes, during the night it's no big deal, however, during the day some people are having some connection issues (unable to renew IP's via DHCP, or unable to find the Profile server or logon server). At first I thought it may have been QOS packets, but NetMon is showing the packets as "Unknown",STP is off, 1GB backbone, 100MB connection to stations, collision blocking is enabled. I know it could be a bunch of things but has anyone else seen this? and what was done? One thing I have noticed is that no matter of time or day, this "Unknown" packet seem to never take more then 10MB of bandwidth?

Any Ideas would be helpfull!

 

[krr]

As you said, it could be a bunch of things.

First: "STP is off". Without Spanning Tree you could have a loop somewhere. Starting with the backbone, disconnect and reconnect one cable after the other and see if the traffic stops. A network diagram would be very helpful here. When you located a switch this way, continue the procedure with all ports on this switch until you find the bad connection.

The facts that all lights are on and that you can see bogus packets on your NetMon tells me that the packets must be Broadcasts or Multicasts. From the trace you can at least see the source MAC address. The first 3 bytes are the vendor id from which you could get a hint what type of interface it could be. In the case of a loop this will not tell you the culprit, only which poor sucker's packet got caught.

I once located a bad print server sending continuously ARP broadcasts on a 100Mbit link, flooding and blocking the whole network. Before I continue telling war stories the disconnect method has proven to be the fastest and most effective.

Cheers *Rob

 

[glen812]

Thank you ROb!
I spent the better part of the weekend adding STP on all Backbone switches. The problem however continued until I released the ARP cache on all backbone switches as well.
STP really helpped out as far as Network performance though.

Thanks again.