Interface errors on one side of fiber link

[tommy_steele]

Hey folks,

I'm seeing interface errors on one side of a fiber link (this is a member of a LAG, but the other member is fine) - please see below.  From this output, can I tell which side of the link the issue is most likely on?  Thanks in advance.

7150_STACK_CORE>show int eth 1/3/2
10GigabitEthernet1/3/2 is up, line protocol is up
Port up for 35 minute(s) 15 second(s)
53575 input errors, 53477 CRC, 0 frame, 0 ignored
4 runts, 91 giants

7150_IDF_STACK>show int eth 1/2/7
10GigabitEthernet1/2/7 is up, line protocol is up
Port up for 19 hour(s) 28 minute(s) 39 second(s)
0 input errors, 0 CRC, 0 frame, 0 ignored
0 runts, 0 giants

[BenBeck · Accepted solution]

The most likely scenario is that 1/2/7 on the IDF side is 'sending' errors to the other side. I would swap that optic and/or check fiber there. 

[BenBeck · Accepted solution]

The most likely scenario is that 1/2/7 on the IDF side is 'sending' errors to the other side. I would swap that optic and/or check fiber there. 

[inphobia · Accepted solution]

swapping transceivers, as proposed, is the best first step. if you don't have any spare ones you can just swap them between the switches (as in, move the one in core to idf & visa versa).
if the errors go away: most likely bad connection
if the errors stop on core but start on idf: most likely bad transceiver
if the errors continue on core swap your fibers. if you're using dac cables i think most of what you can troubleshoot has been done.
if after all this you still get errors on the core you might have an issue with the physical sfp slot.

side note: while giants can usually be explained, in my experience runts tend to be the start of a lot of physical troubleshooting.