For automatic fallback of internet, you need to configure BGP routing protocol for multihoming. If want to do with Static routing, you will have to manually change the NAT statements to allow the PCs to go out to the internet with specific ISPs address.
VPN fallback can be automatic. On the far end PIX, you need to give two peers on the crypto isakmp statements. when one peer goes down IPSEC connectivity will happen through the other Public IP. AT your end router, u will have one default route towards ISP A and a higher metric route towards ISP B.
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...