Cisco IOS

NAT Config Generator

Generate static NAT, dynamic NAT, and PAT configurations

What is NAT?

Network Address Translation (NAT) rewrites IP addresses as packets cross a router. It is most often used so many private hosts can share a small number of public addresses.

Static NAT: one inside IP mapped to one outside IP.
Dynamic NAT: inside hosts take addresses from a public pool.
PAT / Overload: many inside hosts share a single public IP using different source ports.

Inside vs Outside

Inside interface faces the LAN with private addresses.
Outside interface faces the WAN/Internet.
You must mark interfaces with ip nat inside and ip nat outside or NAT will not work.

Typical Use Cases

Goal	Type	Notes
Internet access for office	PAT	Most common, uses one public IP.
Publish internal web server	Static NAT	Server always reachable at same public IP.
Pool of public IPs	Dynamic NAT	Internal hosts borrow from public pool.

NAT Type

Inside Interface

Outside Interface

Inside Network (with wildcard)

conf t
access-list 1 permit 192.168.10.0 0.0.0.255
ip nat inside source list 1 interface Gi0/1 overload
!
interface Gi0/0
 ip nat inside
interface Gi0/1
 ip nat outside
!
end