Lost Carrier on 4506

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Dec 29th, 2009
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I am getting some complaints from users on a telnet app that is breaking. It seems like the session freezes. They get an error. I researched the error and I found that it was a connectivity problem.

So I looked at the interfaces of the switch where these people site. here is an an example:

FastEthernet2/12 is up, line protocol is up (connected)
  5 minute output rate 0 bits/sec, 0 packets/sec
     0 packets input, 0 bytes, 0 no buffer
     Received 0 broadcasts (0 multicasts)
     0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
     0 input packets with dribble condition detected
     418 packets output, 47790 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 babbles, 0 late collision, 0 deferred
     0 lost carrier, 0 no carrier
     0 output buffer failures, 0 output buffers swapped out

Most of the time this is how they look. All the ports look good.

Ocassionnally I see an increment on 1 lost carrier. This happens to all ports on the switch. And then it goes away. I have not been able to correlate the lost carrier increment and the lost telnet session. What does it mean to have a lost carrier? I guess my question is could a lost carrier break a tcp session?



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burleyman Tue, 12/29/2009 - 08:30
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Check for a bad cable. This is usually a physical issue.


pener1963 Tue, 12/29/2009 - 08:37
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Thanks Burleyman for the information.

The odd thing about the 1 Lost Carrier increment is that it is switch wide. In other words, when it happens, it happens to all the ports that are connected at the time except the fiber uplinks. The fiber links do not have any lost carrier increment. It only happens to the copper ports on all blades.

What does this say I cannot be sure. An electrical problem perhaps?

Still I wonder if a lost carrier would break a tcp session?


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