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Supervisor Engine 5 stops to forward traffic in a Catalyst 4500 Switch that runs Cisco IOS Software Releases 12.2(25)EW, 12.2(25)EWA through 12.2(25)EWA4, and 12.2(25)SG


Core Issue

A Catalyst 4500 Switch with the Sup5-10GE Supervisor Engine sometimes stops switching packets. The show cdp neighbors detail shows the switch information but in some scenarios you are unable to Telnet to the device and no traffic goes through.  For example, you experience the of network connectivity.

The problem occurs due to a memory leak of the switching buffers due to parity errors.

You can confirm this memory leak when you look at the output of the show platform hardware interface all command. You see a low FreeListCount value when you have the connectivity problem.

For example:

CAT4510#show platform hardware interface all

Global Hardware Gigaport State
RxIpg : 6
TxIpg : 264
FreeListCount : 329

The typical values of the free list count are between 20,000 and 64,000, which depends on the traffic that is switched. A count of 329 is too low and indicates a memory leak.

The affected releases are Cisco IOS® Software Releases 12.2(25)EW, 12.2(25)EWA through 12.2(25)EWA4, and 12.2(25)SG.

Note: Only Sup5-10GE (WS-X4516-10GE) is affected by this problem.

Refer to Cisco bug ID CSCsb61172 for more information.


As a workaround, reload the Supervisor in order to resolve the problem.

This defect is resolved in Cisco IOS Software Release 12.2(25)EWA5 and later, as well as in Cisco IOS Software Release 12.2(31)SG and later. You can download these software releases from Cisco Downloads.

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