Rapidly incrementing collisions on 4-port ethernet module in 2621

[miker]

I am seeing a severe collision incrementation (10 - 12% of packets) on the ethernet port(s) of a 4-port ethernet add-in module. The two Fast Ethernet ports show no collisions, the device the problematic ethernet port peers to shows a lot of runts. This interface is the outside connection of our boundary router.

Cables have been changed, connections to a different device have been made, different ports on the card have been configured and tested, all with the same result. Surrounding devices have been powered off to minimize EMI, all to no avail. The collision rate remains fairly constant.

I suspect a failing module, but wanted to see if anyone else has experienced similar problems caused by other factors.

Feedback and suggestions are welcome.

[scottmac]

What is connected to the four-port module?

Are the cables "store bought" or handmade? If they're handmade, what pair / color order did you use?

Also check your duplex settings for the ports taking errors: try setting them to a hard value (instead of "auto" - or take it back to "auto if you've got 'em hard set).

High collisions count (*any* collision count on a switch set to full duplex) usually means a duplex mismatch, second to that, incorrect or poorly made (or trashed) cables.

Good Luck

Scott

[miker]

The initial cable was store-bought crossover, but we have also tried one of our own matching handmade - no difference. Duplex settings for both the router port and its peering device (Packeteer packetshaper) are set to 10mb 1/2 duplex. We have tried switching to auto indvidually on both units, as well as together. We have placed a 10mb hub in between, as well as taken all other devices out of the signal path and connected our router to the state's end-node router, so the two routers were peering via the crossover cable. Again duplex and speed settings on both devices were matched. The end-node router was reporting the runts, while ours reported the large number of ongoing collisions.

Thanks for the thoughts...

Mike R.

[jroyster]

hmm...both sides of the link are hard coded/forced to 10/half?

If you are getting a large number of collisions and runts and you have half-duplex this is normally a sign of a very congested link. Basically a runt is the result of a collision and will also fail the FCS check. this is all part of normal 10/half ethernet operation.

but the levels you desribed are VERY high...2-3% collisions are cause for concern.

Any way you can use 100/full or 10/full and take the possibility of a collision out of the picture? I also suggest cables as what you are desribing is strictly physical layer.