FastEthernet is up, line protocol is down

Posted on 2005-04-15
Last Modified: 2013-11-29
Hi there.

I have a Cisco router (IOS12.1) with two FastEthernet interfaces (as well as BRI and Serial) one of which I can no longer connect with.

I did a "show int fastethernet" and it is showing FastEthernet is up but line protocol is down.  It looks like it's been down over a week (from last input/output stats).

What could this be an indication of?  An unplugged cable, bad interface...?  Should I do a shutdown, no shutdown to try to bring it back up?  Could I loose the config doing that?

I don't have local access to the router at present.

As always, any help is greatly appreciated.

Question by:ttist25
    LVL 27

    Accepted Solution

    >>What could this be an indication of?  An unplugged cable, bad interface...?   Yes, it could be any of those - a cabling problem.  Layer 1 problem.

    >> Should I do a shutdown, no shutdown to try to bring it back up?  You can try that.

    >> Could I loose the config doing that? No, but just to be sure, why not do a copy run start first thing you have access to them, unless your policy is to maintin different configs (I've heard of that before).  Or you could tftp the running config to a laptop or something.

    Definitely check the physical cabling.  You might need to take some cable testing equipment with you - like a Time Domain Reflectometer (TDR) if you have on, a wire mapper, or at least some kind of continuity tester if it was a previously working cable.
    LVL 1

    Author Comment

    I'm in a limited, contract, support capacity and am not intimately familiar with the setup so am trying to tread lightly.

    I'll try the shutdown / no shutdown and see if it helps.  I also remember seeing reference to an interface  rest command.  Is this something I should also try?  Can you provide the syntax?

    Thanks for the quick response.
    LVL 32

    Expert Comment

    It also could be a problem on the switch, bad port etc .......  What type of device doe sthis interface connect to?
    Have you looked at the port stats from that device's perspective? errors, config changes, etc .......


    Featured Post

    Better Security Awareness With Threat Intelligence

    See how one of the leading financial services organizations uses Recorded Future as part of a holistic threat intelligence program to promote security awareness and proactively and efficiently identify threats.

    Join & Write a Comment

    Even if you have implemented a Mobile Device Management solution company wide, it is a good idea to make sure you are taking into account all of the major risks to your electronic protected health information (ePHI).
    Meet the world's only “Transparent Cloud™” from Superb Internet Corporation. Now, you can experience firsthand a cloud platform that consistently outperforms Amazon Web Services (AWS), IBM’s Softlayer, and Microsoft’s Azure when it comes to CPU and …
    Viewers will learn how to connect to a wireless network using the network security key. They will also learn how to access the IP address and DNS server for connections that must be done manually. After setting up a router, find the network security…
    After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

    733 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    23 Experts available now in Live!

    Get 1:1 Help Now