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
your 3660, look at the speed and duplex settings for each device connecting
to the etherstack hub. If one of those is miss-configured or possibly has a
failing NIC, bad packets will be transmitted out all ports on the hub and
will show up in the "show int f0/0" output on your router.
Mike Braun
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.
> 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 onI 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.
So thats human error not a problem with using forced settings, eliminate the
human error and I think you'll see forced always works, autoneg sometimes
works. (For future reference dont employ incompetent people to run your networks
folks!)
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.
Heh. I dont want to look at examples or find out what your experience is but in
mine across a wide range of vendors its prone to problems.
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.
Have you looked at what autoneg is.. its horrible, a hack to help out the above
incompetent engineers who dont know how to force duplex.
.. well thats my opinion on the matter anyhow 
Steve
So thats human error not a problem with using forced settings, eliminate the
human error and I think you'll see forced always works, autoneg sometimes
works. (For future reference dont employ incompetent people to run your networks
folks!)
Problem with autoneg is that you always have to have manageble equipment
and you always have to check both ends after changing anything. In an ISP
environment that is generally not a problem luckily, apart from the
equipment you connect to on the customer side, some customers insist on
using cheapo stuff.
Autoneg does add good things, especially on GigE. Autoneg on a GigE yields
the most desireable effect of "link loss return", ie if you lose fiber
link one way the link goes down at both ends.
Have you looked at what autoneg is.. its horrible, a hack to help out the above
incompetent engineers who dont know how to force duplex.
Hmm, I might draw the same conclusion regarding automatic gear boxes on
cars but I think I should not considering the situation in the US
regarding that perticular issue
Personally I think the idea with autoneg is really a good thing, why
shouldnt two units advertise their capabilities and then act accordingly
to what they both can do? We do the same on SMTP (EHLO) and so on.