Thanks for your reply Arthur. This is still proving elusive to setup in practice. I have used the following config on the routers.... I think I still may have it setup incorrectly .
REMOTE SITE
-----------
crypto isakmp policy 1
hash md5
authentication pre-share
crypto isakmp key ####### address x.x.x.x {concentrator public addr}
!
crypto ipsec transform-set to_vpn esp-des esp-md5-hmac
!
crypto map gre 50 ipsec-isakmp
set peer x.x.x.x {concentrator public addr}
set transform-set to_vpn
match address 101
!
interface Tunnel0
ip address 192.168.20.2 255.255.255.0
tunnel source Ethernet0
tunnel destination 10.0.x.x {router addr behind concentrator}
crypto map gre
!
interface Ethernet0
ip address 10.230.x.x 255.255.0.0
no ip route-cache
no ip mroute-cache
crypto map gre
!
interface BRI0
no ip address
encapsulation ppp
dialer pool-member 1
isdn switch-type basic-net3
!
interface Dialer1
ISP dialup blurb
!
ip classless
ip route 0.0.0.0 0.0.0.0 Dialer1
no ip http server
!
!
map-class dialer DialClass
access-list 101 permit gre host y.y.y.y {remotesite public addr} host x.x.x.x {concentrator public addr}
dialer-list 1 protocol ip permit
HQ SITE
-------
crypto isakmp policy 1
hash md5
authentication pre-share
crypto isakmp key ####### address y.y.y.y {remotesite public addr}
!
!
crypto ipsec transform-set to_vpn esp-des esp-md5-hmac
!
crypto map gre local-address Ethernet0
crypto map gre 50 ipsec-isakmp
set peer y.y.y.y {remotesite public addr}
set transform-set to_vpn
match address 101
!
interface Tunnel0
ip address 192.168.20.1 255.255.255.0
tunnel source Ethernet0
tunnel destination y.y.y.y {remotesite public addr}
crypto map gre
!
interface Ethernet0
ip address 10.0.x.x 255.255.0.0
no ip route-cache
no ip mroute-cache
!
ip classless
ip route 0.0.0.0 0.0.0.0 Tunnel0
ip route y.y.y.y {remotesite public addr} 255.255.255.252 z.z.z.z {conc private address}
no ip http server
!
access-list 101 permit gre host x.x.x.x {concentrator public addr} host y.y.y.y {remotesite public addr}
