Weird networking issue.

Tue Jan 7 23:28:20 UTC 2003

At 05:36 PM 1/7/2003, Mikael Abrahamsson wrote:

>On Tue, 7 Jan 2003, Braun, Mike wrote:
>
> > I think we all agree that autonegotiation is evil, and should be avoided
> > whenever possible.  When you are looking for the root cause of the 
> errors on
>
>I don't agree. I have seen more problems generated by incompetence in
>trying to fix duplex/speed, than I have seen problems generated by autoneg
>not working properly.
>
>I am always amazed by the fact that very few people out there know that
>you have to lock duplex at BOTH ENDS of any given link for it to work
>properly.
>
>Generally, in a LAN environment with good quality switches and good
>network cards, autoneg works just fine. Yes, with 10/100 meg
>fiber/converters converters you should definately lock duplex, but in most
>other cases I recommend to leave the duplex setting to auto.
>
>Yes, cisco routers are notoriously bad at doing autoneg, but I blame that
>on cisco and not on autoneg. The el cheapo $50 desktop switches seem to
>hack autoneg just fine.

Of all the gear I've worked with, from a wide variety of vendors, Cisco is 
the clear leader in gear that is incapable of successfully doing 
autonegotiation. I do hope they've improved this in newer products. The all 
time low point for them has to have been the 2924 switch. Putting a 
crossover cable between two 2924's yielded invariably BAD results. Now I 
can forgive engineers for not testing against every brand of router or host 
out there, but at LEAST test against another copy of the same box you're 
building. Not even something to blame on a QA engineer... this should have 
been tested before the box left the engineering benches.

Connections to desktop computers and even servers are often better left set 
for autonegotiation. As people repatch connections to switches, it's easy 
to forget to reconfigure the switch.

All that said, it's been my experience that when Cisco routers are 
involved, you really do have to force the interface settings or tempt fate. 