fast ethernet

Answered Question
May 18th, 2007
User Badges:

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




Correct Answer by mohammedmahmoud about 9 years 11 months ago

Hi,


Kindly check the cables.



HTH, please do rate all helpful replies,

Mohammed Mahmoud.

  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 5 (1 ratings)
Loading.
Correct Answer
mohammedmahmoud Fri, 05/18/2007 - 07:03
User Badges:
  • Green, 3000 points or more

Hi,


Kindly check the cables.



HTH, please do rate all helpful replies,

Mohammed Mahmoud.

ilnaiduccna Fri, 05/18/2007 - 12:26
User Badges:

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.

leungcm Fri, 05/18/2007 - 20:51
User Badges:

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

lleopoldo Fri, 05/18/2007 - 07:12
User Badges:

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.

mohammedmahmoud Fri, 05/18/2007 - 07:21
User Badges:
  • Green, 3000 points or more

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.

scottmac Fri, 05/18/2007 - 08:12
User Badges:
  • Green, 3000 points or more

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


lleopoldo Fri, 05/18/2007 - 10:12
User Badges:

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).

scottmac Fri, 05/18/2007 - 19:40
User Badges:
  • Green, 3000 points or more

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.

lleopoldo Mon, 05/21/2007 - 03:20
User Badges:

Hi Scott,


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

Actions

This Discussion