C1841 fa0/0 up when unplug LAN cable

Answered Question
Dec 20th, 2008
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When I unplug LAN cable from interface fa0/0 why interface still up but protocol down ?


It is default ? or we can set ?


Thank you in advance.

Correct Answer by Richard Burts about 8 years 4 months ago

teerapon


It is the default behavior of IOS routers such as the 1841 that if the FastEthernet interface is not plugged into some device then the interface will show as interface up and line protocol is down.


HTH


Rick

Correct Answer by scottmac about 8 years 4 months ago

If you have keepalives disabled, then the link will stay up.


Check your config, under that interface, for a "no keepalive" statement


Also make sure you are looking at the right interface ....


Good Luck

Scott


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Correct Answer
scottmac Sat, 12/20/2008 - 07:22
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If you have keepalives disabled, then the link will stay up.


Check your config, under that interface, for a "no keepalive" statement


Also make sure you are looking at the right interface ....


Good Luck

Scott


t.sriwetchasin Sun, 12/21/2008 - 18:28
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Thank you Scott.


So, If I used "no keepalive" command under int fa0/0, interface and protocol will up both but I did not plug LAN cable into that interface.


I also check with another new router C1841. After completed boot and no shutdown the fastEthernet interface. FastEthernet interface is up without LAN cable connected.


It may be default of router? and How to make it down when we did not plug the LAN cable into interface ?


Environment

C1841

IOS c1841-ipbasek9-mz.124-23.bin


Thank you.

Correct Answer
Richard Burts Mon, 12/22/2008 - 08:53
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teerapon


It is the default behavior of IOS routers such as the 1841 that if the FastEthernet interface is not plugged into some device then the interface will show as interface up and line protocol is down.


HTH


Rick

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