Error Analysis on a Cisco Switch - Input errors, no output errors 1

[rpreston]

I have a network which runs across 2 Cisco Catalyst 2950 switches.

I have been seeing problems recently with devices dropping off the network for short periods, just long enough for Insight Manager to alert me that they're gone. They return at the next polling interval.

I've looked at the interface stats on the switches and on some ports I'm seeing lots of input errors, mostly CRCs. I'm not seeing any output errors, however. If i had a faulty NIC or cable wouldn't I expect to see a port somewhere with output errors ?

If that's not the case, what kind of problem would cause me to be seeing input errors only on a number of ports, and what tools can I use to go about diagnosing the fault ?


TIA


Rob

 

[vipergg]

If you are seeings errors and crc's on the port the first you have to do is check the speed/duplex settings of the switch against what the pc nic card is set at . If the switch is set as auto for speed and duplex then the pc nic "MUST" be set at auto also , conversly if the switchport is hardcoded at say 100/full duplex then the pc nic card "must" be hardcoded to 100/full . Crc's and errors are usually caused by these type mismatches when have one side hardcoded to a speed and duplex and the other side is set as auto. Do a "show interface status" and this will show you the switchports and how they are set , if they set as auto they will have something like a-100 for the speed , if there is no -a then the speed has been hardcoded.

 

[jneiberger]

Vipergg is correct. This is probably the result of a duplex mismatch. The full duplex side of a mismatched link will see input errors. The half duplex side will see late collisions. Make sure both sides are set to AUTO unless you have a reason for hard-coding your settings, in which case both sides need to be hard-coded.