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New Member

2960 IOS 12.2(55)SE heap fragmentation


I just upgraded the IOS in my 2960's to 12.2(55)SE due to the new SVI static route feature. However, I noticed a serious issue on some of my 2960's:

-the boot failed on one of them, and stopped at the "boot:" prompt. I had to re-issue the boot command via console to start the boot process again, and at this time the boot was succesful.

- even in case of succesful boot, I can see a remark: shadowing for flash filesystem is disabled due to heap fragmentation.

After the boot, there is plenty of free RAM, and big continuous free RAM area. We use only like 2-3 VLANs, SSH, SNMP alerting, PVRSTP, but actually very simple switch config files. Is this a new bug in this release, as the open caveats section has no remark on this?


Everyone's tags (2)

Re: 2960 IOS 12.2(55)SE heap fragmentation


      Can you issue a 'reload' and see if the switch gets stuck in 'switch:' ? If it does, check the boot log for any post failures.(Please post log here)

Have you tried running an IOS in 12.2(50), (52) or (53) and are seeing the same issue?

New Member

Re: 2960 IOS 12.2(55)SE heap fragmentation

I upgraded from 12.2(50)SE, with that I had no such issues.I am planning to reboot some, but only during non-office hours.

Cisco Employee

Re: 2960 IOS 12.2(55)SE heap fragmentation


I agree with Vijay's suggestions.

Regarding the "heap fragmentation" message during the boot, I have actually seen this message on various 2960 series Catalysts running diverse IOS versions (but all fairly recent). While I do not know what that message actually means, I have a feeling that this is not currently related to your problem with booting. I have never ecountered any problems with my 2960 although the message about heap fragmentation does appear on those.

Best regards,



Re: 2960 IOS 12.2(55)SE heap fragmentation

The ' shadow buffering disabled due to heap fragmentation' is usually seen on 2960s during bootup. I think this was ~ 12.2(50)SE onwards.It's not really a bug and is related to the boot process