1) Serial 0 is administratively down, line protocol is down. In this case, the first parameter relates to the physical layer, and if it receives a carrier detect signal yes, the interface is active.
2) If this is a DTE Serial port. In port configuration mode, use no shutdown. the result is as follows:
Serial 0 is up, line protocol is down. this is the physical layer is active. But what does line protocol down mean? Actually, this relates to the data link layer, which looks for keep-alive information from the connecting end (keep-alive information is used between two devices to confirm the availability of connectivity). If the line is active and the protocol is down, then there is a problem with the clock (keep-alive information) or with the framing. It should be due to "clock rate not configured" or "encapsulation type configuration inconsistency" or "bad cable" on the corresponding DCT side. "The cable is bad. This is a data link layer problem.
3) We set in the corresponding DCT side: clock rate 64000. next in the view as follows:
Serial 0 is up, line protocol is up.
4) If we draw a snake, set in the DCT side: encapsulation ppp(frame encapsulation ppp(frame -relay). Then the result on the DTE side is as follows:
Serial 0 is up, line protocol is down. obviously this is a data link layer problem. Because the default encapsulation type on the DTE side is HDLC.
2, show ip interface [int] Provides Layer 3 configuration information for the router interface. This includes interface status, IP address, subnet mask, basic IP information and access lists.
3, show protocols views Layer 1 and Layer 2 connectivity for each port, including IP address status.