A sudden increased of cpu utilization/processing can be anything, i.e PIX handling simultaneous/thousands of attack like DoS/DDoS, viruses, unreachable external syslog server and so on. Hard to pinpoint exact reason, but you need to check the PIX, i.e log entries for a clue, connection (who has highest no of connection and using which port, like 1 IP having hundreds of connected ports) and many more.
CPU utilization depends on how intensive of traffic inspection need to be performed by PIX. Basically, PIX handling bigger network with thousands on of clients probably has higher CPU utilization compared to smaller network with small no of traffic.
But at any time, it probably should not exceed 40% or even less.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...