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Hello, my name is tyler and I'm new to this forum. A problem with an hp switch has me stumped, and I'm hoping someone here has seen it before. Thanks in advance for any advice you can offer!

I've got an HP procurve 2524 switch that was having "excessive crc/alignment" and "blocked by LACP" errors on port 13. As the frequency of the errors increased, the computers and ip phones would experience increasing packet loss, eventually losing connectivity completely.

Thinking it was a cabling problem or a virus, I looked up the mac addresses that were connected to port 13. One of the devices on this port had a mac address starting with 00:0a:57, which is the identifier for HP, but the only HP device on our network is the switch itself. When I disconnected the cable from port 13 of the switch, the "crc errors" and "blocked by LACP" errors stopped, and the network started working smoothly. The devices whose MAC addresses had been listed on port 13 still had connectivity after the cable was removed. Their MAC addresses moved to other ports on the switch. After removing the cable, the mysterious second HP MAC address disappeared.

The wiring at this location is a tangled nightmare, which left me wondering if this could have been caused by one port of the switch being connected to another of it's own ports... Has anyone run into a problem like this before?
 

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I think connecting a switch port to another one could create problems, I confess I've never tried it!

... time passes ...

And the answer is YES! That really screws things up! Apparently, the first broadcast message that comes along gets stuck running around and around. I plugged two ports together, and suddenly I had LOTS of network traffic. :grin:
 

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In my experiance of 2524s (on the default settings ie medium sensitivity, no spanning tree etc) a "loop" will totally kill your network. I work in a school so kids like to try this one as they know it will shut down the network. Set security to High sensitivity and alls fine, the switch detects the loop and shuts them ports down.
 
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