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Router produces no output when the show run command is issued

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Core Issue

This is due to a lack of available memory caused by insufficient physical memory or a memory leak.

Resolution

If no output is produced when the show run command is issued, perform the following steps:

  1. Issue the show memory [summary] command to see how much free process memory is available as well as the size of the largest free contiguous memory block.
router#show memory summary
            Head         Total(b)    Used(b)     Free(b)     Lowest(b)    Largest(b)
Processor   616970C0     9867072     8746428     1120644     37076        58144
     Fast   616770C0     131080      74616       56464       56464        56412

In the previous example, the free processor memory is more than 1MB (1,120,644 bytes) but the largest memory block is only about 58K (58144 bytes).

This indicates the memory is fragmented. This may be caused by a bug. If either the Free(b) or the Largest(b) numbers are low, the show run command output may not be produced due to a lack of available memory to process the command.

  • Check the logs for %SYS-2-MALLOCFAIL error messages by issuing the show logging command. Note: If logging is enabled for the terminal session, the %SYS-2-MALLOCFAILmessage may show up when the show run command is issued.
    router#show logging
    Syslog logging: enabled (0 messages dropped, 0 flushes, 0 overruns)
         Console logging: disabled
         Monitor logging: level debugging, 0 messages logged
         Buffer logging: level informational, 280 messages logged
         Trap logging: level informational, 1259 message lines logged
             Logging to 159.161.30.53, 1259 message lines logged
             Logging to 143.91.102.84, 1259 message lines logged

    If the %SYS-2-MALLOCFAIL errors are present, refer to Troubleshooting Memory Problems. This is also useful for determining whether the issue is caused by a lack of physical memory or a software issue.

    If a memory leak or other bug is causing the issue, upgrade the Cisco IOS  Software to a version in which the issue is resolved.

    If the router does not have enough physical memory, either add memory or change to a version of Cisco IOS Software with a lower memory requirement.

    In cases where a memory leak is present, a temporary workaround may be to reload the router.

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