If you're running 6.3 code on the PIX then enable the following command:
fixup protocol icmp-error
If you don't have this command then you have to allow the return ICMP packets back through the PIX, as th ePIX does not open holes for return ICMP traffic. Add the following line to your existing outside access-list:
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...
[toc:faq]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 and UDP are I...