Serial interface state is down, but protocol not down

[rakuten02]

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."

[Georg Pauwen]

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 ?

[rakuten02]

Thanks for confirming !

This is a real router, not simulated.

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

[rakuten02]

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