7206 Router / PA-T3 / DS3 / Serial Interface Down Question

[slade]

We had a brief outtage and a sh log showed this:

*Mar 9 22:57:43.349 UTC: %LINK-3-UPDOWN: Interface Serial1/0, changed state to down

*Mar 9 22:57:44.533 UTC: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial1/0, changed state to down

We are trying to figure out what caused the interface to change state to down. After it came back up, we yanked a cable out of the PA-T3 adapter, plugged it back in and looked at the log. The exact same message sequence was logged. What can we make of this? Assuming the cable and adapter is in good condition, will we get the same error if our provider has a hiccup? I was under the impression that the serial line status would stay 'up' regardless of cable status, but that is not the case. Any pointers greatly appreciated.

[deilert]

When your serial interface looses carrier detect your link will go down . When your router misses 3 keepalives over a serial line this will cause the line protocol to go down , You can have a condition if your router is still rx carrier detect but it misses 3 keepalives , this will give you an up/down condition.

What caused this , more than likely a problem with your local exchange carrier .