Solutions to Cisco router port faults

CSU ── channel server unit, DSU ── data server unit
1. Serial * is down, line protocol is down (DTE)
Faults:
[1] No power is added to the vro.
[2] LINE is not connected to CSU/DSU.
[3] hardware error.
Solution:
[1] Check power supply.
[2] Check whether the cables and serial ports used are correct.
[3] switch to another serial port.
2. Serial * is up, line protocol is down (DTE)
Faults:
[1] local or remote router configuration is lost.
[2] The remote router is not powered on.
[3] line faults and switch faults.
[4] The serial sending clock is not set on CSU/DSU.
[5] CSU/DSU fault.
[6] local or remote router hardware faults.
Solution:
[1] Set MODEM, CSU, or DSU to "LOOPBACK", and run the "show int s *" command to check whether line protocol is UP. If it is UP, it indicates that the mailbox Bureau is faulty or the remote router has been shut down.
[2] If the remote router fails, repeat step [1].
[3] Check whether the serial port connected by the cable is correct. Use "show controllers" to check which cable is connected to which serial port.
[4] type "debug serial interface". If line protocol does not come up, or the number of activated ports does not increase, it indicates that the router hardware is incorrect and the router port is changed; if line protocol is UP and the number of activated ports increases, the fault is not on the local router.
[5] Change the router port.
3. Serial * is up, line protocol is down (DCE)
Faults:
[1] CLOCKRATE in router port configuration is lost.
[2] The DTE device is not started.
[3] Remote CSU/DSU faults.
[4] cable connection error or fault.
[5] router hardware error.
Solution:
[1] add CLOCKRATE to the router port configuration.
[2] set the DTE device to SCTE mode.
[3] confirm that the cables used are correct.
[4] If line protocol is still DOWN, replace the router port.
4. Serial * is up, line protocol is uplooped)
Faults:
If a LOOP exists in a line and the sequence number in the activated software package changes to a random number at the beginning, a LOOP is generated if the same random number is returned to the LOOP Line.
Solution:
[1] use the "sh run" command to find LOOPBACK.
[2] use "no loopback" to remove the LOOP.
[3] If PROTOCOL is still DOWN, contact the post office.
5. Serial * is up, line protocol is down (disabled)
Faults:
[1] Postal Bureau fault.
[2] CSU/DSU hardware faults.
[3] router hardware faults.
Solution:
[1] Find the dual-state component signal of CTS or DSR.
[2] Do loopdte loop with CSU/DSU). If the fault persists, it may be a hardware fault. If the fault stops, it turns out that it is a fault of the post office.
[3] replacing the faulty hardware.
6. Serial * is administratively down, line protocol is down
Faults:
[1] PORT may be shut down.
[2] duplicate IP addresses.
Solution:
[1] use the "no shutdown" command to remove SHUTDOWN.
[2] change one of the duplicate IP addresses.