For a complete configuration of NAT/PAT with a diagram for visual assistance, see the sample configuration at the end of this chapter.
Step 1: Define a static route on the remote router stating where public addresses should be routed.
ISP(config)#ip route 184.108.40.206 255.255.255.255.128 s0/0
Informs the ISP router where to send packets with addresses destined for 220.127.116.11 255.255.255.255.128
Step 2: Define a pool of usable public IP addresses on your router that will perform NAT.
Private address will receive first available public address in pool
Corp(config)#ip nat pool scott 18.104.22.168 22.214.171.124 netmask 255.255.255.128
Defines the following:
Name of pool is scott (The name of the pool can be anything.)
Start of pool is 126.96.36.199
End of pool is 188.8.131.52
Subnet mask is 255.255.255.128
Step 3: Create an ACL that will identify which private IP addresses will be translated.
Corp(config)#access-list 1 permit 172.16.10.0 0.0.0.255
Step 4: Link the access control list (ACL) to the pool of addresses. (Create the translation.)
Corp(config)#ip nat inside source list 1 pool scott
The source of the private addresses is from ACL 1
The pool of available public addresses is named scott
Step 5: Define which interfaces are inside (contain the private addresses).
Router(config)#int fa 0/0
Router(config-if)#ip nat inside
You can have more than one inside interface on a router. Addresses from each inside interface are then allowed to be translated into a public address
Step 6: Define the outside interface (the interface leading to the public network).
Router(config)#int s 0/0
Router(config-if)#ip nat outside