serial and line protocol

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Aug 13th, 2008
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what happens when line protocol is down and serial is up and vice versa?


what happens when both are down?


Please share the troubleshooting steps as well if possible.


Thanx in advance!

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Richard Burts Wed, 08/13/2008 - 09:33
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Faizan


If the interface state is up but the line protocol is down it indicates some problem or mismatch in configuration between the two ends of the link. Here are some things to check when you get an up/down state:

- is there correct clocking on the circuit? lack of clocking will make the line protocol go down.

- is the encapsulation configured the same on both ends? If one is HDLC and the other is PPP it will force the line protocol to go down.

- are keepalives configured on both ends or not configured on both ends? If one end is configured with keepalives and the other end is not configured with keepalives it will force the link protocol to go down on the end that is configured with keepalives.


If the interface state is down but the line protocol is up that is an invalid state. If you see it there is probably a bug in the code. You should then plan a code upgrade to a version that does not have this bug.


If the interface state is down and the line protocol is down then it indicates a problem with the connection of the serial interface. Check for something to be unplugged, or perhaps a bad cable, or perhaps the CSU/DSU being powered down.


HTH


Rick

Faizan Shaikh Wed, 08/13/2008 - 09:42
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Rick,


"If the interface state is down but the line protocol is up that is an invalid state. If you see it there is probably a bug in the code. You should then plan a code upgrade to a version that does not have this bug."


What exactly do u mean by code here?

Richard Burts Wed, 08/13/2008 - 09:51
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Faizan


In this case the code here is the IOS operating system that runs the router.


HTH


Rick

Faizan Shaikh Wed, 08/13/2008 - 09:57
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Rick,


Thanx a ton for such a genius reply!


one more thing can u explain me abt the clocking on the circuit in brief?



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