Excessive late collisions

[Frank Gilsdorf]

Hi all,

I have some problems with HP-Workstation connected to a ProCurve Switch 2424M.

If I'm transferring date for example with ftp I get "Excessive late collisions" messages on the switch.

lanadmin reports many FCS Errors. And I get only 8K/s.

Here is the lanadmin output:

Ethernet-like Statistics Group

Index = 1
Alignment Errors = 711
FCS Errors = 1436
Single Collision Frames = 0
Multiple Collision Frames = 0
Deferred Transmissions = 0
Late Collisions = 0

And yes, Auto-Sensing is switched off.

Frank

[Sanjay_6]

Hi Frank,

Try this link,

http://us-support3.external.hp.com/cki/bin/doc.pl/sid=2703984018293f7a8d/screen=ckiDisplayDocument?docId=200000049067570

It suggests, flush 2424M to factory defaults.

hope this helps.

Regds

[Helen French]

Hi,

Late collisions occur when a collision occurs after 64 bytes or more has been transmitted. It is the same as a normal collision except it happens later in the transmission.

This can be caused by lan cables which are too long, or too many repeaters/hubs between nodes. Also caused by a bad interface card or transceiver, which does not listen (Carrier Sense) before transmitting.

Check this thread for more information:

http://us-support3.external.hp.com/cki/bin/doc.pl/sid=6650a9d416995a1002/screen=ckiDisplayDocument?docId=200000024624770

HTH,
Shiju

[Darrell Allen]

Hi Frank,

Although auto-sensing is off, have you verified the speed / duplex setting on the NIC and the switch port? Use lanadmin -x PPA# on the HP.

It could be a physical problem.

Darrell

[Ron Kinner · Accepted solution]

It looks to me like you have full duplex on your end and the switch has half duplex on its end. You have no collisions on your end but the switch sees collisions. When the switch starts to transmit and then your end starts to transmit too the switch detects what it thinks is a collision and stops transmitting in mid packet. This causes you to receive a lot of broken packets which show up as incoming errors of all types.

It's not enough to disable autonegotiate on your end. Has to be done on both ends.

Ron

[Frank Gilsdorf]

Thank you for your fast help.

I switched off Auto-Sense on the switch and now it works!

But I don't know why? I thinked if one side is "hard-coded" the other side is able to use auto-sensing. Any ideas???

Thanks
Frank

[Darrell Allen]

In a perfect world, you could force one side and set the other to autoneg and things would work fine. Unfortunately, that's not the case in the real world.

I strongly suggest that for servers you always force the speed / duplex setting on both the NIC and switch port.

I can't explain the problem. I just know it is a problem.

Darrell

[Ron Kinner]

I read somewhere that the stupid specifications for autonegotiate forbid it from going to full duplex except when the other side is also autonegotiating. Otherwise it's stuck at half even if it knows that the other side wants full. I never looked it up to verify but I've seen many cases which proved that that is how most autonegotiate works.

Ron