Cisco NAT Fundation

                      Topology

1. DNAT (Dynamic)

int fa0/0

　　ip nat inside

int fa0/1

　　ip nat outside

ip nat pool ISP-POOL 198.51.100.3 192.51.100.14 netmask 255.255.255.240

ip nat inside source list 1 pool ISP-POOL

access-list 1 permit 10.1.1.0 0.0.0.255

show ip nat translations

2 SNAT (Static)

ip nat inside source static 10.1.1.1 198.51.100.3

ip nat inside source static 10.1.1.2 198.51.100.4

3 PAT (Port Address Translation)

int f0/0

　　ip nat inside

int f0/1

　　ip nat outside

ip nat inside source list 1 interface fastethernet0/1 overload

access-list 1 permit 10.1.1.0 0.0.0.255

show ip nat translations

4 NVI (NAT Virtual Interface)

int f0/0

　　ip nat enable

int f0/1

　　ip nat enable

NOTE: The NAT Vitrual Interface feature can be used with a Dynamic NAT configuration or a PAT configuration , but it is not supported with a Static NAT configuration. Not all platforms and Cisco IOS versions since Cisco IOS Release 12.3(14)T support the NAT Virtual Interface feature . Therefore , the ip nat enable command might not be accepted on your device , even though you are running Cisco IOS Release 12.3(14)T or later . 

Cisco NAT Fundation

原文：http://www.cnblogs.com/zhnhelloworld/p/5632249.html