Troubleshooting guide

3. Troubleshooting Functional Failures During Operation
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(1) Checking the device failure log
One probable cause of disabled communication is a line failure (or damage). The following
describes the procedure for displaying the messages that indicate a hardware failure. You
can find these messages in the device failure log displayed by the Switch.
For details about the contents of the device failure log, see the Message Log Reference.
1. Log in to the Switch.
2. Use the
show critical-logging operation command to display the device failure
log.
3. Each entry in the device failure log indicates the date and time that a failure occurred.
Check whether a device failure log entry was displayed for the date and time that
communication was disabled.
4. For details about the failure and corrective action for the device failure log entry
described above, see the Message Log Reference, and then follow the instructions
given in the manual.
5. If a Switch failure log entry was not displayed for the date and time when
communication was disabled, see
(2) Checking the interface status.
(2) Checking the interface status
Even when the Switch hardware is operating normally, a fault could have occurred on the
hardware of a neighboring device connected to the Switch.
To check the status of the interface between the Switch and the neighboring device, do the
following:
1. Log in to the Switch.
2. Use the
show ip interface operation command to check whether the status of the
interface with the target neighboring device is
Up or Down.
3. If the status of the target interface is Down, see
3.4 Network interface
communication failures.
4. If the status of the target interface is Up, see
(3) Identifying the range for a failure
(from the Switch).
(3) Identifying the range for a failure (from the Switch)
If a failure has not occurred on the Switch, a failure might have occurred somewhere on the
route between the Switch and the remote devices. To identify the range for a failure in order
to determine the fault location on the route, do the following:
1. Log in to the Switch.
2. Use the
ping operation command to check the communication with the two remote
devices that are unable to communicate. For details about examples of using the
ping operation command and how to interpret the execution result, see the
Configuration Guides.
3. If communication with the remote devices cannot be verified by the
ping operation
command, execute the command again to check communication with each of the
devices up to the remote device, beginning with the device closest to the Switch.
4. If the execution result of the ping operation command indicates that the failure
occurred on the neighboring device, see
(5) Checking the ARP resolution
information with a neighboring device. If the execution result indicates a failure on
the remote device, see
(6) Checking the unicast routing information.
(4) Identifying the range for a failure (from a customer's terminal)
To use the customer's terminal to identify the range for a failure so that you can determine
the fault location on the route with a remote device in an environment in which login to the