The following is a partial output of the show interfaces command:

What does the Serial 0 is up, line protocol is down statement signify in the output? (Choose all that apply.)

A.
the shutdown interface command is present in the router configuration

B.
a cable is unplugged

C.
the interface is displaying normal operation

D.
there are no problems with physical connectivity

E.
there is a configuration problem in the local or remote router

Explanation:
The Serial 0 is up, line protocol is down statement in the output signifies the following:
There are no problems with the physical connectivity.
There is a configuration problem in the local or remote router.
The remote router might not be sending the keep-alives.
There may be a problem with the leased lines such as line noise and a malfunctioning switch.
There is an incorrect configuration of the CSU/DSU, which can cause timing issues on the cable.
The local or remote CSU/DSU might have failed.
The option stating that the shutdown interface command is present in the router configuration is incorrect
because if the shutdown interface command is present in the router configuration, the message displayed
would be Serial 0 is administratively down, line protocol is down.
The option stating that a cable is unplugged is incorrect because that would be indicated by Serial 0 is down,
line protocol is down. Physical problems such as a bad cable or cable unplugged are addressed in the first part
of the output (serial0 is up/down).The option stating that the message refers to normal operation of the interface is incorrect because the line
protocol is shown as down, which indicates a problem.
Objective:
Routing Fundamentals
Sub-Objective:
Troubleshoot basic Layer 3 end-to-end connectivity issues