!
version 12.2
no service pad
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname 831-uut1
!
memory-size iomem 10
!
ip subnet-zero
!
ip audit notify log
ip audit po max-events 100
!
crypto isakmp policy 1
encr 3des
authentication pre-share
crypto isakmp key grel address 100.1.1.1
!
crypto ipsec security-association lifetime seconds 86400
!
crypto ipsec transform-set strong esp-3des esp-sha-hmac
!
crypto map mymap local-address Ethernet1
crypto may mymap 1 ipsec-isakmp
set peer 100.1.1.1
set transform-set strong
match address 151
!
!
!
!
interface Tunnel0
ip address 1.1.1.1 255.255.255.0
tunnel source Ethernet1
tunnel destination 100.1.1.1
crypto map mymap
!
interface Ethernet0
ip address 202.2.2.2 255.255.255.0
hold-queue 100 out
!
interface Ethernet1
ip address 100.1.1.1 255.255.255.0
crypto map mymap
!
ip classless
ip route 200.1.1.0 255.255.255.0 Tunnel0
ip http server
!
!
access-list 151 permit gre host 100.1.1.2 host 100.1.1.1
!
line con 0
no modem enable
stopbits 1
line aux 0
line vty 0 4
!
scheduler max-task-time 5000



===========
The following example shows IPSec configuration on a Cisco 837 router.

version 12.2
no service pad
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname 837-uutl
!
memory-size iomem 10
!
mmi polling-interval 60
no mmi auto-configure
no mmi pvc
mmi snmp-timeout 180
ip subnet-zero
!
ip audit notify log
ip audit po max-events 100
ip ssh time-out 120
ip ssh authentication-retries 3
!
crypto isakmp policy 1
encr 3des
authentication pre-share
crypto isakmp key grel address 100.1.1.1
!
crypto ipsec transform-set strong esp-3des esp-sha-hmac
!
crypto map mymap local-address ATM0
crypto map mymap 1 ipsec-isakmp
set peer 100.1.1.1
set transform-set strong
match address 151
!
interface Tunnel0
ip address 1.1.1.1 255.255.255.0
ip mtu 1440
tunnel source ATM0
tunnel destination 100.1.1.1
crypto map mymap
!
interface Ethernet0
ip address 202.2.2.2 255.255.255.0
hold-queue 100 out
!
interface ATM0
ip address 100.1.1.2 255.255.255.0
no atm ilmi-keepalive
pvc 1/40
protocol ip 100.1.1.1 broadcast
encapsulation aa15snap
!
dsl operating-mode auto
crypto map mymap
!
ip classless
ip route 200.1.1.0 255.255.255.0 Tunnel0
ip http server
ip pim bidir-enable