Which show interfaces command output indicates that the link may not be functional due to a Data Link layer
issue, while the Physical layer is operational?
A.
Ethernet 0/0 is up, line protocol is up
B.
Ethernet 0/0 is up, line protocol is down
C.
Ethernet 0/0 is down, line protocol is up
D.
Ethernet 0/0 is down, line protocol is down
Explanation:
The first or left-hand column (Ethernet 0/0 is up) indicates the Physical layer state of the interface, while the
second or right-hand column (line protocol is down) indicates the Data Link layer state of the interface. The
following command output excerpt indicates that the link is not functional due to a Data Link layer (or “line
protocol”) issue, while the Physical layer is operational:
Ethernet 0/0 is up, line protocol is down
If the problem were at the Data Link layer while the Physical layer is operational, the show interfaces command
output will indicate that the interface is up, but the line protocol is down.
In the normal operation mode, when both Physical layer and Data Link layer are up, the show interfaces output
will display the following message:
Ethernet0/0 is up, line protocol is up
The message Ethernet 0/0 is down, line protocol is up is not a valid output.
The message Ethernet 0/0 is down, line protocol is down indicates that both the Physical layer and the Data
Link layer are down. Therefore, this is an incorrect option.
Objective:
LAN Switching Fundamentals
Sub-Objective:
Troubleshoot interface and cable issues (collisions, errors, duplex, speed)