Network question

[Tom Peters]

At 08:29 PM 12/31/2006 -0600, you wrote:
>You wrote...
>>Just trying to figure out why a 2 GHz box is getting consistently
>>beaten by a 225 MHz one.
>
>This sounds like the classic problem of a duplex mismatch between the 
>device and the hub. A lot of folks don't realize it, but when you mix 
>10mb/HDX/100mb/FDX devices in a single network - you would THINK that the 
>devices would autonegotiate identical settings on both ends. C'mon, they 
>even SAY they autonegotiate on the box, and they DO have an 'auto' 
>setting, right? Fact is, they get it wrong better than 80% of the time. 
>Even two devices from the same manufacturer usually don't autonegotiate 
>right. Pretend that "autonegotiation" doesn't exist. Set both ends 
>manually to identical settings. If one
>
>Some will say - this can't be... I plug them in and they work, and the 
>right speed lights come on! And they pass traffic JUST fine. Don't trust 
>this. FDX/HDX mismatches can create very odd looking wierdness. Like a 
>connection that SEEMS to work, but is actually working very poorly.
Yeah, I can attest. We used to have one particular run of 3Com cards that 
negotiated  the wrong duplex about 25% of the time when used with one 
particular kind of 10/100 blade in a Cisco Catalyst 5000 series switch. The 
symptoms were that the connection would work ok, and ping tests seemed to 
indicate all was well, but as you loaded the connection down a little, it 
would start having errors and retries, until the retries overwhelmed any 
real work being done.

Any time someone reported a good connection that would hang, timeout, and 
quit with errors whenever you tried to copy a file over it (larger than a 
few k) I know what the problem was.

A firmware upgrade fixed some of it. Policy fixed the rest: Thou shalt set 
the speed and duplex we tell you to on your PC, or we'll disable your port. 
No Auto/Auto permitted. Better gear and Corporate Standard NICs eliminated 
the problem after a while.




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