There are some NAT commands that are involved in an access-list change, like NAT0ACL and policy NAT. In these 2 cases, a change in the access-lists implicitly changes the rules of the NAT, and a 'clear xlate' is required. Refer usage guidelines of http://www.cisco.com/en/US/docs/security/fwsm/fwsm22/command/reference/c.html#wp1217767. Generally this can also happen when the ip addresses are not available for translation. If this is the case you can consider implementing PAT.
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...