View the port status of the vro to resolve network faults.

You may often encounter various router problems when working on network engineering. However, in addition to the configuration of a router, a more common method is to view network faults through the router port status. The following is a summary of my experience and I hope it will be useful to you.

Check the status of the vro. The most important thing is to check the serial and portocol statuses of the vro. When we # show interface-number in the vro privileged mode, the following status appears:

1. Serial interface-number is down, line protocol is down

Possible problems: the router is not powered on; LINE is not connected to CSU/DSU; hardware error.

Solution: Check the power supply, check whether the cables and serial ports used are correct, and switch to other serial ports.

2. Serial inface-number is up, line protocol is down (DTE)

Possible problems: local or remote router configuration is lost; remote router is not powered on; line failure, switch failure; Serial Port sending clock is not set on CSU/DSU; CSU/DSU failure; local or remote router hardware faults.

Solution: Set MODEM, CSU, or DSU to "LOOPBACK" and run the "show int Serial interface-number" command to check whether line protocol is UP, it indicates that the communication board is faulty or the remote router has been shut down. Check whether the SERIAL port connected by the cable is correct. Use "show controllers" to check which cable is connected to which SERIAL port. 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 up, the number of activated ports increases, proving that the fault is not on the local router; change the router port.

3. Serial interface-number is up, line protocol is down (DCE)

Possible problems: CLOCKRATE loss in the vro port configuration; DTE device not started; remote CSU/DSU faults; cable connection errors or faults; and router hardware errors.

Solution: Add clockrate to the vro port configuration, set the DTE device to SCTE mode, and check whether the cables used are correct. If the line protocol is still DOWN, change the vro port.

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