[c-nsp] Negotiation problem with Catalyst 2950 and Cisco 2821

[Jay Hennigan]

Ted Mittelstaedt wrote:

>Hi All,
>
>  I hae a stock 2821 router with 2 gig E ports on the inside,
>and 2 load-balanced t1's going to the Internet, running NAT.
>IOS version is 12.4.5
>
>  I have several 2950's don't know what version of firmware
>(probably old).
>
>  I plug the 2821 into the 2950s and set the 2821 and 2950 to 
>autonegotiate speed and duplex.
>
>  The 2821 negotiates to 10 base T half duplex.  Users
>report problems with intermittent disconnects and slowness
>when surfing the web, etc.
>
>  I go to Goodwill, no less, and purchase a 10 year old 8
>port dumb hub, 10BaseT only.  Not a switch.  Cost is $7.99
>
>  I insert this hub between the 2821 and the Catalyst 2950.
>
>  Problems of disconnects and slowness go away.
>
> Speculation, anyone?
>  
>
Duplex negotiation mismatch.  Fairly common.  Cisco has used a
variety of chipsets for ethernet ports over the years.  Many of
them seem to not play well with others.  You're probably seeing
a lot of collisions and runt errors on the interfaces.  Seeing
as the layer 1 connection between these devices isn't likely to
change, why not set both devices for the best throughput, in
this case 100 mbits/s, full-duplex? 

Then you can donate that extra 10-base-T hub to the Goodwill.