This problem is observed in these conditions:
This slow, constant memory leak happens in the Cisco Express Forwarding (CEF) IPC Background in function fib_memory_alloc_named_internal. This happens only if IP routing is disabled.
The workaround for this problem is to enable IP routing with the use of the ip routing global configuration command, and to reload the switch stack.
This issue is documented in Cisco bug ID CSCsc59027.
This issue is resolved in these Cisco IOS software releases, which can be downloaded from Cisco Downloads. Upgrade to any of these releases for a permanent workaround:
Refer to Troubleshooting Memory Problems for more information.