Question

Device attached to Cisco 2950G floods our network with bad packets

Asked by: RAMCIT

Hello Experts,
We have just had a nightmarish scenario with our network. The symptoms began as loss of packets on all facets and locations of our LAN. Initially we thought it was out 50MB Metro-Ethernet connection that links both WANS, so we tried to isolate it as such with no luck. After starting to monitor our Cisco 2950 switches, I noticed that on our main gigabit switch, one of the ports was showing thousands of erroneous packets in the "port statistics" section under the "Total Transmit Errors" column. We proceeded to change the device from that port to another, with the erroneous packets continuing to be sent through the new port. Finally, we unplugged the server from the switch altogether and all of our connectivity problems disappeared.

My question is, how could one server connected to one port on this Cisco switch cause ALL of our LAN to go down?
I would think that these switches are "smart" enough to catch this and deal with it appropriately.

Thanks very much for your input!

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Asked On
2007-04-26 at 15:13:25ID22537232
Tags

cisco

,

devices

,

port

Topics

Cisco PIX Firewall

,

Network Operations

,

Network Switches & Hubs

Participating Experts
1
Points
500
Comments
3

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Answers

 

by: lrmoorePosted on 2007-04-26 at 17:04:16ID: 18986085

They are smart enough, but the "smarts" are not enabled by default.
You might want to enable storm-control on all interfaces.
Switch# configure terminal
Switch(config)# interface gigabitethernet0/1
Switch(config-if)# storm-control broadcast level 20  <= if b'cast traffic is > 20%
Switch(config-if)#storm-control action shutdown

20120131-EE-VQP-002

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