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CPU utilization of The ASA 5520 in my company suddenly increased to 98% for 2 hour. In this time, I have checked the logs:


Deny TCP reverse path check from to on interface inside

I canceled download in a PC, then the problem is resolved.

Could you please tel me what should I do that I will not faced with this problem for future.

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migrated from Aug 21 '13 at 6:24

This question came from our site for information security professionals.

Questions about general computing hardware and software are off-topic here, but can be asked on Super User. – Lucas Kauffman Aug 21 '13 at 4:44

That's not the entire log message, and that's not necessarily the main cause of your CPU problems.

PIX/ASA messages each have a unique code, in this case it's %PIX-1-106021 which you can look up in the documentation (e.g for v6.3).

Similarly if you look up reverse path check you will see that this problem is cause by either your firewall topology or routing being wrong, or a spoofed external IP address on the inside.

The trivial solutions (turn off verify with no ip reverse-path on an interface, or turn off that log message with no logging message 106021) are usually a bad idea.

This is probably a better starting point: PIX/ASA: Monitor and Troubleshoot Performance Issues

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