Re: Asymetric network speed question

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Tim <ignored_mailbox@xxxxxxxxxxxx> wrote:

On Tue, 2006-07-04 at 22:46 -0600, David G. Miller wrote:

Could a bad cable cause this or is it the skge module on bend (spindle
and mutilate both run CentOS 4.3 with the sk98lin module and iperf
says the speed is about the same in both directions between them)?  A
bad cable seems odd given the speed is fine in one direction.

It is possible to be a cabling issue.  You could have a problem with its
wiring for data in one direction (there's two pairs for each direction).

Obviously you don't want to pull more cable through, but you can test
with loose wire through the room between the machines.  If that acts
differently, try reterminating your other wire, one end at a time.  I'd
still suggest testing with another cable rather than just reterminating
it.  You eliminate the cable, itself, as a fault, that way.

Swapping a NIC might be in order, too.

Did some patch cable swapping and the problem stays with the workstation. I even put one of the "slow in one direction" patch cables between the server and the wall jack and I get symmetric speed between the server and the old PIII/733 box. I also swapped which wall jack the workstation is plugged into to see if its the wire inside the wall. No difference in behavior. I guess next thing is to try a different NIC in the workstation and see if its the NIC. The NICs were surplussed to me from where I used to work so I can't complain too much if I have trouble with them. They probably wouldn't have gotten rid of them unless there was a reason.

BTW, gigabit uses all four wire pairs in the cable. Just something to keep in mind. Lots of folks have gotten used to 100BASE-T only using two pairs.

Cheers,
Dave

--
Politics, n. Strife of interests masquerading as a contest of principles.
-- Ambrose Bierce


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