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