topic Re: Speed Duplex - Switch to Switch in Switches, Hubs, and Modems

Speed Duplex - Switch to Switch

Bergin — Wed, 07 Feb 2007 14:02:22 GMT

Hi,

I have two 2524's that are connected together via a Cat 5 cable - currently both ports are set to AUTO and I can't see what its using.

I flipped one of the switches to 100 FDX and then I get errors:

Excessive CRC/Alignment errors
Excessive late collision detected

I set it back to Auto and the events go away.

So my questions are - what should the two ports be set to for a Cat5 uplink - auto and auto or 100 FDX and 100 FDX?

And if I leave them at Auto - what speed/duplex are they autonegotiating at?

Thanks,

Rob

Re: Speed Duplex - Switch to Switch

rick jones — Wed, 07 Feb 2007 21:25:50 GMT

Leave them at auto. Likely as not they are running at 100 Mbit and full duplex.

If there is no way at the switch to see the actual port characteristics (I find that surprising - the manuals at http://www.hp.com/go/procurve may be of help there) then you can do something like run some netperf TCP_STREAM tests across that switch to switch link. If you see speed in excess of 10 Mbit/s you know the link is 100mbit. If you see no collisions in the port stats you can pretty much know that it is running full-duplex - even a "unidirectional transfer" with TCP will generate _some_ collisions (not late collisions - those are different and poorly named) with the ACK's flowing back from the receiver.

I've attached some boilerplate on autoneg which you may find helpful and explain some of what you were seeing.

Re: Speed Duplex - Switch to Switch

Richard Brodie_1 — Thu, 08 Feb 2007 08:26:55 GMT

"I have two 2524's that are connected together via a Cat 5 cable - currently both ports are set to AUTO and I can't see what its using."

show interface brief

Re: Speed Duplex - Switch to Switch

Bergin — Thu, 08 Feb 2007 14:03:34 GMT

Thanks all, the "Show Interfance Brief" does list the current Speed/Duplex and I did leave them both at auto.

Thanks,

Rob