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rakuten02
Beginner

Serial interface state is down, but protocol not down

In the logs, a serial interface belonging to a router is down, "Interface Serial1/0, changed state to down". 

But there isn't a corresponding "Line protocol on Interface Serial1/0, changed state to down" which I would normally expect after the first log message of "interface changed state to down".

 

Does this mean that for Serial1/0, the line is down but protocol is still up ? What could have caused this ?

 

The interface went back up after a few seconds based on the logs. "Interface Serial1/0, changed state to up."

3 REPLIES 3
Georg Pauwen
VIP Master

Hello,

 

the interface state is the physical layer, if that is down, there is, in theory, no way for the line protocol to NOT be down.

Is this a 'real' router, or a simulator ? How is the serial interface configured ?

Thanks for confirming !

This is a real router, not simulated.

I will get back again regarding the configuration of the interface.

The interface is a PPP link, will there be any info you'll need ?