Does the internal host you're trying to ping have a route to the pool of addresses, and does this route eventually point back to the PIX (if the default gateway of this internal host is the PIX then that should be sufficient). If the number of encrypted packets on the PIX is staying at 0, then this indicates that the PIX is not seeing the reply from the internal host (check routing as I mentioned), or your nat 0 is incorrect.
Can you post the config, making sure to xxxx out your passwords and external IP addresses?
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...