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New Member

is up, line protocol is down

I've got a 2801 sitting here.

When I 'sh int', both FastEth interfaces show "interface is up, line protocol is down".

The thing is, nothing is plugged into either one... Shouldn't they both be down/down due to physical issue?

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Accepted Solutions
Hall of Fame Super Silver

Re: is up, line protocol is down

Tyler

It is a subtle difference between router code and switch code.

HTH

Rick

10 REPLIES
New Member

Re: is up, line protocol is down

"interface up" means it is admined up. Do a "shutdown" command on the interface and it will show as down/down.

Hall of Fame Super Silver

Re: is up, line protocol is down

Tyler

Actually for Ethernet/FastEthernet interfaces it is normal for them to show as up/down when nothing is plugged in. Is it just that it is different from what you expected, or is there some problem involved with this?

Kristen

If you do a shutdown on the interface it will show as admin down, which is not quite the same as down/down.

HTH

Rick

New Member

Re: is up, line protocol is down

Yep, you're right Rick. I forgot about that. :)

New Member

Re: is up, line protocol is down

Thanks for the quick replies.

With nothing plugged in, I was expecting down/down....

When will an interface show down/down (not admin down/down)???

I thought that the first up/down was the physical layer status, and the line protocol was the layer 2 status...

Hall of Fame Super Silver

Re: is up, line protocol is down

Tyler

What you describe (interface up/down is the physical layer and line protocol up/down is the layer 2 status) is the case for most serial interfaces. It is not the case for Ethernet/FastEthernet interfaces. I am not sure what it would take for an Ethernet/FastEthernet to show down/down.

HTH

Rick

New Member

Re: is up, line protocol is down

Thanks for the reply.

Interesting.

Why does a switch show down/down on fastethernet interfaces when nothing is plugged in, then?

Hall of Fame Super Silver

Re: is up, line protocol is down

Tyler

It is a subtle difference between router code and switch code.

HTH

Rick

New Member

Re: is up, line protocol is down

Thanks for your help rburts!

Hall of Fame Super Silver

Re: is up, line protocol is down

Tyler

I am glad that my information has been helpful. Thank you for using the rating system to indicate that your question was resolved (and thanks for the rating). It makes the forum more useful when people can read a question and can know that they will read responses which did resolve the question.

The forum is an excellent place to learn about Cisco networking. I encourage you to continue your participation in the forum.

HTH

Rick

Re: is up, line protocol is down

This is interesting conversation.

On the other hand, if you disable "keepalive" in the router ethernet interface, both physical and protocol will show up/up

Regards,

Dandy

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