目的：1.1.1.1和4.4.4.4互相通信
要求：R2，R3不能配置路由和NAT

R1=======================================
int lo 0
ip add 1.1.1.1 255.255.255.255

int f0/0
no sh
int f0/0.12
en do 12
ip add 12.1.1.1 255.255.255.0

ip route 4.4.4.4 255.255.255.255 12.1.1.2

R2============================================

int f0/0
no sh
int f0/0.12
en do 12
ip add 12.1.1.2 255.255.255.0
ip policy route-map A

int f0/0.23
en do 23
ip add 23.1.1.2 255.255.255.0
ip policy route-map B

access-list 1 permit 1.1.1.1
access-list 4 permit 4.4.4.4

route-map A permit 10
match ip address 1
set ip next-hop 23.1.1.3

route-map B permit 10
mat ip add 4
set ip next-hop 12.1.1.1

R3===========================================

int f0/0
no sh
int f0/0.23
en do 23
ip add 23.1.1.3 255.255.255.0
ip policy route-map A

int f0/0.34
en do 34
ip add 34.1.1.3 255.255.255.0
ip policy route-map B

access-list 1 permit 1.1.1.1
access-list 4 permit 4.4.4.4

route-map A permit 10
mat ip addres 1
set ip next-hop 34.1.1.4

route-map B permit 10
mat ip add 4
set ip next-hop 23.1.1.2

R4==============================================
int lo 0
ip add 4.4.4.4 255.255.255.255

int f0/0
no sh
int f0/0.34
en do 34
ip add 34.1.1.4 255.255.255.0

ip route 1.1.1.1 255.255.255.255 34.1.1.3