Cat5500 speed negotiation

Unanswered Question
Apr 4th, 2007
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We have a strange problem with our Cat5513.

We get really bad upload speed whenever we hard-coded the port on Cat5500 to 100mb full-duplex.

It gets about 19mb/s download and 18mb/s upload when it's on auto negotiation, however it only gets about 789kb/s upload speed when it is hard-coded to 100mb full. It seems like it's only affecting upload speed since it gets about 17mb/s download speed.

What gives???

Do we have a faulty switch? or buggy CatOS?

Thank you

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Craig Balfour Wed, 04/04/2007 - 07:12
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You've given the speed and duplex configuration for the Cat5500 port but what is the speed and duplex configuration on the remote side?

If both sides are set to auto-negotiate then they should negotiate 100 Mbit/s full duplex and everything should be fast.

However, if the Catalyst 5500 is hard set to 100 Mbit/s full duplex and the remote side is set to auto-negotiate, negotiation will fail and the remote side will probably settle on 100 Mbit/s half duplex. This would be duplex mismatch which will definately cause a slowdown in speed between the two devices and you should also see the error counters climbing on the interfaces.

donglee36 Wed, 04/04/2007 - 08:49
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Thanks for your writing.

We didn't see any error or collision on the ports, and we had same result when we hard-coded 10mb/s full on each side.

Thank you

glen.grant Wed, 04/04/2007 - 11:25
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Both sides must match , if one side is auto then the other side must be auto/auto . If you hardcode one side 100/full then you "must" hardcode the other also , anything else will give you speed/duplex mismatches .


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