[c-nsp] Speed Issues

John Neiberger John.Neiberger at efirstbank.com
Thu Feb 2 13:44:34 EST 2006

>>> "Case Hugo" <cisco at elkgrove.net> 2/2/06 11:15:47 AM >>>
>(Hope this is addressed to the right forum)
>The issue we are seeing is that when we do a speed test behind a Cisco
3550  and then a 3640 to the internet we see approriate speeds (8-10
>but if we do a speed test from behind the 3550 to a server between the
3550 and the 3640 we get a download speed of about 80kps (ouch).  When
>replace the 3550 with a cheap router the speed is normal.  So I
programmed the 3550 incorrect.  Where did I go wrong? What am Iooking
for?  (I 
>checked the speed and duplex of all ports. All set to 100 & full)

There's your problem. Hard-setting your speed and duplex is a very bad
idea. In this particular case, I would bet that the interface facing the
server is seeing a lot of input errors and the interface on the server,
if you could see the stats, is seeing late collisions. The problem is
that some devices still participate in auto negotiation even when you
have manually configured the speed and duplex. If they don't detect an
autonegotiating link partner they will assume that they're connected to
a hub and drop back to half duplex, which results in a duplex mismatch.

Configure *both* sides to AUTO and all should be well.


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