I understand you are wondering if the VPN 3000 can provide GRE/IPSec services. Unfortunately the VPN 3000 cannot provide GRE encapsulation services, it can only provide IPSec tunnels. If you wish to run GRE traffic over an IPSec tunnel terminated on a VPN 3000 that is fine, except that the GRE traffic needs to be terminated on a device which supports GRE, for Cisco that would be a Router running IOS.
The VPN 3000 is an end of life product no longer receiving software development and as such will never support provided GRE services.
What you can do is have two routers and the VPN 3000 to provide GRE/IPSec. How you would do this is to
1. Configure a Lan to Lan tunnel between the outside router and the VPN 3000. The proxies, crypto map acl, will be permit gre between the physical source IP and the destination router.
Lan to Lan tunnel configuration example for IOS and VPN 3000
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...