Do this on both routers.
! define hash and authentication for IKE
crypto isakmp policy 1
hash md5
authentication pre-share
crypto isakmp keepalive 30 5
! define ipsec hash and encryption
crypto ipsec transform-set myset esp-3des esp-md5-hmac
! define neighbor ipsec device, apply ipsec and interesting traffic
crypto map mymap 1 ipsec-isakmp
set peer [neighbor ip]
set transform-set myset
match address 100
! define ACL
access-list 100 permit ip [source network] [destination network ]
! apply ipsec to the egress interface.
interface s0/0
ip address x.x.x.x x.x.x.x
crypto map mymap
