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New Member

fast ethernet

Dear Sir,

we get following error on the fast ethernet. we show interface

-----

FastEthernet0/0 is up, line protocol is down

----

do you know why the protocol down? how do we fix it? please advise.

Best regards

CM Leung

1 ACCEPTED SOLUTION

Accepted Solutions

Re: fast ethernet

Hi,

Kindly check the cables.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

9 REPLIES

Re: fast ethernet

Hi,

Kindly check the cables.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

New Member

Re: fast ethernet

Hi mohammed

His problem with line protocol so when line protocol is down there problem with mismatch config only like (encapsulation, duplex, port settings etc.,)

So Mr. CM Leug plz once cross check your configurations at both ends should be same.

New Member

Re: fast ethernet

Dear Sir,

Thank you fro your input. The root problem is the cable issue. We re-connect the cable the interface is up again. thanks for your value input.

Best regards

CM Leung

New Member

Re: fast ethernet

Where is the fastethernet connected to? If protocol is down, there is mismatch to duplex mode and speed between the fastethernet port and to where it is connected to. Serial up means you got a signal from the interface where you are connected with; line protocol down - means you have mismatch config.

Please rate this if it helps.

Thanks.

Re: fast ethernet

Hi,

After checking the cables please do check the speed, as speed mismatch causes the link to no longer function. (Speed mismatch happens only if statically misconfigured on both ends), while duplex mismatch results in performance-related issues rather than resulting in no connectivity.

HTH, please do rate all helpful replies,

Mohammed Mahmoud.

Green

Re: fast ethernet

You either have a straight-through cable where a cross-over is needed

or

A cross-over cable where a straight-through is needed

or

Someone has configured your FastEthernet interface for a strange/unsupported encapsulation.

Speed and / or Duplex will not cause this error.

Good Luck

Scott

New Member

Re: fast ethernet

Hi Scott,

A wrong cable will make your serial "down", not up. His problem is the protocol is down which is related to duplex/speed or port configuration (access or trunk and encapsulation).

Green

Re: fast ethernet

We've seen instances where the wrong flavor of cable has caused an Up/Down...it might have been an old switch or combination of old/new, I don't recall.

Agreed that "Protocol Down" is probably a bad encaps ... but it's almost certainly not a speed / duplex thing.

New Member

Re: fast ethernet

Hi Scott,

Yes, you're right. I just made simulation test and you are correct. Thanks for the info.

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