R1(config)# crypto isakmp policy 1
R1(config-isakmp)# encryption 3des
R1(config-isakmp)# hash sha
R1(config-isakmp)# authentication pre-share
R1(config-isakmp)# group 2
R1(config-isakmp)# lifetime 86400

R1(config)# crypto isakmp key cisco address 1.1.1.2
R1(config)# crypto isakmp keeepalive 30 periodic

• The peer’s pre shared key is set to cisco.

R1(config)# access-list 101
R1(config-ext-nacl)# permit ip 10.10.10.0 0.0.0.255 20.20.20.0 0.0.0.255

R1(config)# crypto ipsec transform-set IPSEC esp-3des esp-md5-hmac

R1(config)# crypto map CRYPTMAP 1 ipsec-isakmp
R1(config-crypto-map)# set peer 1.1.1.2
R1(config-crypto-map)# set transform-set IPSEC
R1(config-crypto-map)# match address 101

R1(config)# interface GigabitEthernet0/0
R1(config-if)# crypto map CRYPTMAP

• Configuring Site to Site IPSec VPN Tunnel Between Cisco Routers