I'm siting behind left PIX with VPN Client. If I configure left PIX to do address hiding with range of addresses (NAT) I CAN established the tunnel. But if I configure left PIX to do address hiding with one address (PAT) I CAN NOT establish the tunnel. In that case I receive in syslog form left PIX "Deny inbound (no xlate) protocol udp/500 on interface outside".
You should check syslog messages from your 800 Router doing NAT.
In "IPSec VPNs in depth" document, there is a good explanation of using NAT after IPSec, and there Cisco says that some devices do not handle properly VPNs if PAT is used (are we speaking here of Cisco routers and PIX firewall?).
Another possibility is to try IPSec over TCP, but I did not manage to do it. What should I configure on right PIX in order to achiueve this.
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...