Links between 3750 and 2950 input crc errors

[smolz]

We replaced some 3550's with 3750's and now I am seeing input crc errors on multiple ports that are connected to 2950's. I have tried all combinations of duplex/speed settings and replaced cables, I have even moved ports. I keep getting input crc errors building on the 3750 interfaces.

[Georg Pauwen]

Hello,

are you using SFP to GBIC connections ? Have you replaced those as well ? And which fiber are you using MultiMode or SingleMode ?

The input and CRC errors could come from one of the endstations, although that is not very likely, since this problem appears to have started after you replaced the switches.

You might want to turn of keepalives and CDP on the links on which you see the errors, see if that makes a difference.

You could also monitor your network to see where the errors come from. There is a 30-day trial version fo SolarWinds Orion, which you could install, here is the link:

Orion Network Performance Monitor

http://www.solarwinds.net/Orion/Index.htm

Regards,

GP

[andrew.butterworth]

There is a bug on the 3560/3750 (plus 2970 etc) where interfaces configured as 802.1q trunks (or ports configured with Voice VLANs) display inconsistent stats.

For trunk ports or access ports configured with 802.1Q tagging, inconsistent statistics might appear in the show interfaces counters privileged EXEC command output. Valid 802.1Q frames of 64 to 66 bytes are correctly forwarded even though the port LED blinks amber, and the frames are not counted on the interface statistics. There is no workaround. (CSCec35100).

I saw this earlier in the year with Voice VLAN's configured (Nortel IP Phones) - I actually saw the counters CRC increase and the orange LED blink on the ports.

This issue is resolved in later code (12.1(20)EA1 and later).

HTH

Andy

[smolz]

The links are just 100mb copper links, and I am running 12.2(25)SEB2 code.

[Georg Pauwen]

Hello,

ok. Can you try and configure the ports connecting the switches with ´switchport nonegotiate´, thereby disabling any DTP packets ?

Regards,

GP