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The Catalyst 4500 series switch that runs Cisco IOS software reboots with the "%% Low on memory; try again later" error message and has connectivity issues


Core issue

The Catalyst 4500/4948G that runs Cisco IOS Software Release 12.2(25)EWA7 shows these symptoms:

  • ARP is not resolved for directly connected devices, which affects connectivity, and the routing protocols do not form adjacency due to this problem.

  • If Unidirectional Link Detection (UDLD) aggressive is enabled, ports err-disable due to UDLD. These messages appear:

    %UDLD-4-UDLD_PORT_DISABLED: UDLD disabled interface Gi3/1, unidirectional link detected

    %PM-4-ERR_DISABLE: udld error detected on Gi3/1, putting Gi3/1 in err-disable state

    In some cases, the UDLD error are seen when you reboot a Catalyst switch. This is expected as the switch is processing a lot of control packets, for example, spanning tree, CDP, trunking, and so forth, and can miss a few UDLD keepalives.


    Note: The UDLD is just a symptom of the switch that does not process frames and not the cause. Hence, if you disable UDLD, it does not make a difference.

  • A slow memory leak is another symptom.  These are the messages with tracebacks:


    %SYS-2-MALLOCFAIL: Memory allocation of 784 bytes failed from 0xXXXXXX, alignment 8
    Pool: Processor Free: 36 Cause: Not enough free memory Alternate Pool: None
    Free: 0 Cause: No Alternate pool -Process= "", ipl= 0, pid= 49 -Traceback=0xXXXXXX

This issue is documented in Cisco bug ID CSCsh25687.


This issue is resolved in Cisco IOS Software Release 12.2(25) EWA8, which can be downloaded from Cisco Downloads.

Refer to Understanding and Configuring the Unidirectional Link Detection Protocol Feature for more information.

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