what could be the reason?

Unanswered Question
Nov 30th, 2008

Whenever leased line goes down, Both Serial Interface & Line Protocol goes down. What could be the reason?

I have this problem too.
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johnlloyd_13 Sun, 11/30/2008 - 02:05

it could be a lot of reasons. one could be at layer 1 problem. can be cabling or power problem on the device. could be a layer 2/3 issue, where there's a change in the config either from telco/ISP or from your end.

thotsaphon Sun, 11/30/2008 - 04:28

hi vinoth,

it should be layer1 problems. f.e. Clock provided by ISP's modem is stoped somehow. or Cable problems.


Giuseppe Larosa Sun, 11/30/2008 - 11:20

Hello Vinoth,

this behavior may be the result of the DCE configuration (DSU): it can be configured to provide the CD signal (CD raised) only if receiving the CD on the service provider link.

If so on the router you see the interface that goes down / down.

If instead the DCE is configured to provide CD signal regardless of the state of the wan link you can see a serial interface on the router up line protocol down.

For example in our networks we have links behaving following the first case and other links that follow the second case.

Hope to help



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