Networking - IOS and Security Device Manager - Discussion

Discussion Forum : IOS and Security Device Manager - IOS and Security Device Manager (Q.No. 5)
5.
What layer of the OSI model would you assume the problem is in if you type show interface serial 1 and receive the following message? "Serial1 is down, line protocol is down."
Physical layer
Data Link layer
Network layer
None. It is a router problem.
Answer: Option
Explanation:
If you see that a serial interface and the protocol are both down, then you have a Physical layer problem. If you see serial1 is up, line protocol is down, then you are not receiving (Data Link) keepalives from the remote end.
Discussion:
2 comments Page 1 of 1.

Eswar said:   10 years ago
The serial link is available in routers, so routers available in the network layer, then how it is in a physical layer?

Subu said:   10 years ago
Serial link is used to transfer the signals from router to router so signals, voltages are part of the physical layer.

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