NAT overload - ( PAT)

NAT overload 

NAT: Network Access Translation

PAT: Port Access Translation 

How to configure NAT overload (PAT)  on a Cisco router, to allow  all the devices with private IPs  inside  the LAN network to access the INTERNET via one public IP.

the below configuration was applied on CISCO Router 888EG

• Subnet LAN:  192.168.55.0   255.255.255.0

• Public IP :  2.2.2.2  255.255.255.252

• LAN interface Vlan1  ( connected to the private Network )

• WAN Interface serial 0/1 (connected to the WAN cloud or INTERNET )

Configuration:

Router(config)# access-list 10 permit 192.168.55.0 0.0.0.255

Router(config)# ip nat pool SA 2.2.2.2 netmask 255.255.255.252

Router(config)#ip nat inside source list 10 pool SA overload

Router(config)#interface Vlan1    ( LAN  interface )

 ip address 192.168.55.2 255.255.255.0

 ip nat inside

 ip virtual-reassembly in

 ip tcp adjust-mss 1000

 load-interval 30

Router(config)#interface serial 0/1  ( WAN interface )

 ip address 172.19.108.238 255.255.255.252

 ip nat outside

Verifying NAT:


Router# show ip nat statistics
   (this command will show all active translation entries ,   NAT configuration parameters, IP addresses in the pool &  total number os assigned IP addresses)

Router# show ip nat translations  

 ( it will enable verify the correct  NAT translations )

Router# show ip nat translations verbose

  ( it will  provides you with more data includes creation dates and usage of each translation).

Router# clear ip nat translation 

( to clear NAT translation )

Router# debug ip nat  

( to verify NAT live operation ) 

 
Router# debug ip nat detailed 

 ( to verify NAT live operation with more Data )