Do you mean to to capture the packets from a particular source once they reach the firewall or do you want to know IF a packet with this specific source IP would come will it be allowed through?
For the first you have the capture command on the FWSM AFAIK. For the second command there is no 'automated' process on the FWSM. On the ASA/PIX there is! Its called the 'packet-tracer' command. On the FWSM you can just check the ACL applied on that interface manually.
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...