in a traditional site to site tunnel, either side can negotiate the tunnel if traffic that matches the crypto access lists necessitates it to. if you configure an IOS device as an easy vpn server, and the pix the client, then the pix would be in the position to initiate the tunnel. only pix 501 and 506's can be easy vpn clients though.
there are some ways to create tunnels from behind a pix. a site to site tunnel, or a end user client tunnel?
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...