Symbol-Err

[Kevin Dorrell]

I have some Cat 4503 switches (S2+) linked via 1000BaseSX connections. One switch is at the centre with a WS-X4306 card, and another three uplink to it via their supervisor cards.

I did a show interface counters all recently, and I notice a large number of Symbol-Err on all the links, on both sides of each link. I think the links are working OK but there is some rumour that the users are finding the network slow from time to time.

Now, I have read about symbol errors, and I think I understand what they are. But why should I be getting so many of them? I'm talking of counts in the 10**5 to 10**9 over a period of just a few weeks.

I also have a couple of old Cat 4003 switches linked to the centre in the same way. At the central switch, these links also show symbol errors, but at the Cat 4003 end, nada. (Looking at show counters, counter #32).

Any ideas anyone?

Kevin Dorrell

Luxembourg

[Prashanth Krishnappa]

Symbol-Err are seen when the Mac sees "invalid" symbols. In most cases, this is a physical problem - Gbics, fiber, etc. These errors also increment when the link is not up because the Mac isn't syncronized and receives noise.

Also what IOS are you running. We had a cosmetic IOS bug in older code

http://www.cisco.com/cgi-bin/bugtool/onebug.pl?bugid=CSCec07464

[Kevin Dorrell]

Thanks, but I'm not sure it is that one. I am running 12.2(18)EW2, which isn't in the "affected versions" list. I notice that the counts are not incrementing at the moment, so they may be left over from during the installation. I shall clear the counters and see how things develop. I don't think it could be physical because it happens on all the links - unless of couse the cablers made a consistent mistake throughout the building.

I shall be updating the IOS again soon anyway because of another issue (counting half-duplex collisions as errors). As soon as that is fixed, I shall update.

Thanks again.

Kevin Dorrell

Luxembourg

[Richard Burts]

I had a somewhat similar situation in which a switch was showing symbol errors. But the switch connected at the other end of the link was not showing errors. After much confusion and frustration we investigated the fiber path and discovered a bad splice on one of the fibers which explained why we had a one way problem. One switch transmitted clean (so it did not see output errors) but the signal degraded in transit producing some symbol errors but not enough to take down the link. Transmission in the other direction was clean end to end.

My suggestion is to look for physical layer issues in your problem.

HTH

Rick