IPSec을 통한 L2TP(Layer 2 Tunneling Protocol) 구성

Current configuration:
!
version 12.2
service timestamps debug datetime msec localtime show-timezone
service timestamps log datetime msec localtime show-timezone
service password-encryption
!
hostname LAC
!
enable password  7 094F471A1A0A
!

!--- Usernames and passwords are used !--- for L2TP tunnel authentication.

username LAC password 7 0107130A550E0A1F205F5D
username LNS password 7 001006080A5E07160E325F

!--- Username and password used for authenticating !--- the dial up user.

username dialupuser password 7 14131B0A00142B3837
ip subnet-zero
!

!--- Enable VDPN. 

vpdn enable
vpdn search-order domain
!

!--- Configure vpdn group 1 to request dialin to the LNS, !--- define L2TP as the protocol, and initiate a tunnel to the LNS 20.1.1.2. !--- If the user belongs to the domain cisco.com, !--- use the local name LAC as the tunnel name.

vpdn-group 1
 request-dialin
  protocol l2tp
  domain cisco.com
 initiate-to ip 20.1.1.2
 local name LAC

!

!--- Create Internet Key Exchange (IKE) policy 1, !--- which is given highest priority if there are additional !--- IKE policies. Specify the policy using pre-shared key !--- for authentication, Diffie-Hellman group 2, lifetime !--- and peer address.

crypto isakmp policy 1
authentication pre-share
group 2
lifetime 3600
crypto isakmp key cisco address 20.1.1.2 
!

!--- Create an IPSec transform set named "testtrans" !--- with the DES for ESP with transport mode. !--- Note: AH is not used.

crypto ipsec transform-set testtrans esp-des 
!

!--- Create crypto map l2tpmap (assigned to Serial 0), using IKE for !--- Security Associations with map-number 10 !--- and using "testrans" transform-set as a template. !--- Set the peer and specify access list 101, which is used !--- to determine which traffic (L2TP) is to be protected by IPSec.

crypto map l2tpmap 10 ipsec-isakmp 
set peer 20.1.1.2
set transform-set testtrans 
match address 101
!
interface Ethernet0
ip address 10.31.1.6 255.255.255.0
no ip directed-broadcast
!
interface Serial0
ip address 20.1.1.1 255.255.255.252
no ip directed-broadcast
no ip route-cache
no ip mroute-cache
no fair-queue

!--- Assign crypto map l2tpmap to the interface. 

crypto map l2tpmap
!
interface Async1
ip unnumbered Ethernet0
no ip directed-broadcast
encapsulation ppp
no ip route-cache
no ip mroute-cache
async mode dedicated
peer default ip address pool my_pool
ppp authentication chap
!

!--- Create an IP Pool named "my_pool" and !--- specify the IP range. 

ip local pool my_pool 10.31.1.100 10.31.1.110
ip classless
ip route 0.0.0.0 0.0.0.0  Serial0

!--- Specify L2TP traffic as interesting to use with IPSec. 

access-list 101 permit udp host 20.1.1.1 eq 1701 host 20.1.1.2 eq 1701
!

line con 0
exec-timeout 0 0
transport input none
line 1
autoselect during-login
autoselect ppp
modem InOut
transport input all
speed 38400
flowcontrol hardware
line aux 0
line vty 0 4
password 

Current configuration:
!
version 12.2
service timestamps debug datetime msec localtime show-timezone
service timestamps log datetime msec localtime show-timezone
service password-encryption
!
hostname LNS
!
enable password 7 0822455D0A16

!--- Usernames and passwords are used for !--- L2TP tunnel authentication.

username LAC password 7 0107130A550E0A1F205F5D
username LNS password 7 120D10191C0E00142B3837

!--- Username and password used to authenticate !--- the dial up user.

username dialupuser@cisco.com password 7 104A0018090713181F
!

ip subnet-zero
!

!--- Enable VDPN.

vpdn enable
!

!--- Configure VPDN group 1 to accept !--- an open tunnel request from LAC, !--- define L2TP as the protocol, and identify virtual-template 1 !--- to use for cloning virtual access interfaces.

vpdn-group 1
 accept-dialin
  protocol l2tp
  virtual-template 1
 terminate-from hostname LAC
 local name LNS


!

!--- Create IKE policy 1, which is !--- given the highest priority if there are additional IKE policies. !--- Specify the policy using the pre-shared key for authentication, !--- Diffie-Hellman group 2, lifetime and peer address.

crypto isakmp policy 1
authentication pre-share
group 2
lifetime 3600
crypto isakmp key cisco address 20.1.1.1 
!
!

!--- Create an IPSec transform set named "testtrans" !--- using DES for ESP with transport mode. !--- Note: AH is not used.

crypto ipsec transform-set testtrans esp-des 
!

!--- Create crypto map l2tpmap !--- (assigned to Serial 0), using IKE for !--- Security Associations with map-number 10 !--- and using "testrans" transform-set as a template. !--- Set the peer and specify access list 101, which is used !--- to determine which traffic (L2TP) is to be protected by IPSec.

crypto map l2tpmap 10 ipsec-isakmp 
set peer 20.1.1.1
set transform-set testtrans 
match address 101
!
interface Ethernet0
ip address 200.1.1.100 255.255.255.0
no ip directed-broadcast
no keepalive
!

!--- Create a virtual-template interface !--- used for "cloning" !--- virtual-access interfaces using address pool "mypool" !--- with Challenge Authentication Protocol (CHAP) authentication.

interface Virtual-Template1
ip unnumbered Ethernet0
no ip directed-broadcast
no ip route-cache
peer default ip address pool mypool
ppp authentication chap
!
interface Serial0
ip address 20.1.1.2 255.255.255.252
no ip directed-broadcast
no ip route-cache
no ip mroute-cache
no fair-queue
clockrate 1300000

!--- Assign crypto map l2tpmap to the interface. 

crypto map l2tpmap
!

!--- Create an IP Pool named "mypool" and !--- specify the IP range.

ip local pool mypool 200.1.1.1 200.1.1.10
ip classless
!

!--- Specify L2TP traffic as interesting to use with IPSec. 

access-list 101 permit udp host 20.1.1.2 eq 1701 host 20.1.1.1 eq 1701
!
line con 0
exec-timeout 0 0
transport input none
line aux 0
line vty 0 4
password 
login
!
end