NAT example for the Cisco IOS

PAT

interface FastEthernet0/0
ip address 20.20.20.1 255.255.255.0
ip nat outside
!
interface FastEthernet0/1
ip address 192.168.1.1 255.255.255.0
ip nat inside
!
access-list 1 permit 192.168.1.0 0.0.0.255
ip nat inside source list 1 interface FastEthernet0/0 overload

Static PAT

interface FastEthernet0/0
ip address 20.20.20.1 255.255.255.0
ip nat outside
!
interface FastEthernet0/1
ip address 192.168.1.1 255.255.255.0
ip nat inside
!
ip nat inside source static tcp 192.168.1.10 80 20.20.20.1 80