Network cards/switches -- Auto negeoiate vs. forced 100FDx?

[Peter A. Berger Jr.]

Hi all, was wondering if you could all clear up some myths floating around my office.

What is the best practice for speed between network cards and switches -- forced 100 Full Duplex on both sides, or Auto on both sides? (in regards to normal LAN operation and tape backups over the LAN)

My colleagues seem to think that the old problems from the 1980's with the 3Com NICs still applies. I would dissagree, with the current ProCurve technology and current 10/100/1000 card technology I would assume that AUTO would be the best way to go?

Any thoughts/excperience on this issue? Thanks.

[Stuart Teo · Accepted solution]

We have over 10,000 nodes and we have some (perhaps 1-2%) switches nailed at a fixed speed because of a bad negotiation implementation in the past.

However, I've been setting everything to auto negotiate for the last 5 years and not not seen any bad negotiations since.

Well, not true. I have seen 1 model of HP e-PC running Redhat 9 not being able to auto-negotiate with a Procurve 4000. The PC-side chipset is 3COM. The same model running Windows negotiate fine. So it's the way the OS' drives the 3COM chip.

I'm even going full auto on fiber ports. I think it's important not to nail the speed for fiber port because if we have 1 strand of the fiber pair fail, the switch on 1 end will see the failure. The switch on the other end will not. Auto negotiate will solve this problem.

[Jerome Henry]

From all the networks I set up exeprience, auto is a good solution. If any of the device can't, for any reason, go to 100 speed, auto allows it down, whereas 100 forced just prevents it from functionning.

Could be that the old 3Com trouble still remains, I'm not aware anyway of it on my RH9 pcs running 3Com. Can be card model or driver used in previous post. I feel that nowadays, after almost 15 years on 3Com chips, this problem can be solved in any case...

hth

J