Duplex Issue

[bbinion80]

I have a 4507 and I have the ports configured for full duplex.  The routers connected are also set for full but for some reason, the switch keeps negotiating to half-duplex.  Maybe this is a common issue with an easy fix but I can't seem to figure it out. 

Thanks

[glen.grant · Accepted solution]

    That usually means that the switch is set as auto negotiate.  If it was actually hardcoded it could  'not" negotiate to half duplex.  Check your switch settings they should be set as   " speed 100 , duplex full .   Neither the speed or duplex can be set as auto.

[bbinion80]

Thanks for your help guys...

I did have the speed set to auto.  Once I set the speed, the ports reset to full.  I don't think I've had to do that before but I honestly can't remember.  Anyway...thanks ain for your help.

[Joseph W. Doherty]

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Posting

If one side is auto, and the other is full, the auto side should set itself to half, i.e. that's normal/expected behavior.

Again, though, generally current recommendations are auto/auto both sides unless you know it doesn't work.  Disenabling auto gives up some error protection.

Years ago, when auto was "new" it often didn't work correctly, so hard coding became the "norm".

[Umesh Shetty]

Hi Joseph,

I am quit interested in learning what are the benifits of having auto as against hard coded speed/duplex settings. From a technical point of view if I were to suggest the ideal settings what poits can I list down to support my suggestions.

Thnaks

Umesh

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

As noted in the post you replied on, my understanding is auto provides some additional error detection.  I don't have all the particulars, but as one example, some time back, had an Ethernet port set to auto that came on-line "slower" than expected.  Basic cable tester said everything was fine.  Advanced cable tester revealed patch cable was "flaky".  Auto detected there was a link quality issue and then tried to obtain the best working setting.

It also, on some equipment, may allow auto-MDX/MDIX.

[Joseph W. Doherty]

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

That sounds unusual.  If both sides are hard coded duplex, neither side should be changing its duplex setting.  (Unless something with using strait-thru cable?)

Is there a reason why you're unable to use auto on both sides?