Overloading NAT with PAT

PAT – Port Address Translation

• To support lots of inside local IP addresses with only a few inside global, publically registered IP address. NAT overload uses PAT. Instead of just translating the IP address, it also translates the port number.

PAT

Router (config) # ip nat inside source list 1 pool hcl overload

                             # Ip nat pool hcl 200.0.0.1 200.0.0.2 netmask 255.255.255.0

                              # Int e 0

                              # Ip nat inside

                              # Int s 0

                              # Ip nat outside

                              # Debug ip nat (* telnet from source)

                              # show ip nat translations

Dynamic NAT

• Sets up a pool of possible inside global address and defines criteria for the set of inside local IP addresses whose traffic should be translated with NAT.
• Address is dynamically assigned.

Router (config) # access-list 1 permit192.168.10.0   0.0.0.255

Router (config) # ip nat inside source list 1 pool hcl

Router (config) # ip nat pool hcl 200.0.0.1   200.0.0.5 netmask 255.255.255.0

Router (config) # int e 0

Router (config) # ip nat inside

Router (config) # int s 0

Router (config) # ip nat outside

                          # Debug ip nat (* ping from source)