NAT (Network Address Translation) Natting means "Translation of private IP address into public IP address ". In order to communicate with internet we must have public IP address.

Types of NAT:- 1. Dynamic NAT 2. Static NAT 3. PAT

Dynamic NAT:- Many privates IP addresses is mapped to many of IP addresses. One to one Mapping. Advantage is it provides only security. Disadvantages are we need to buy many public IP which is equal to private IP.(Expensive) It provides only one way access. From inside to outside access is allowed. Outside to inside access is not allowed.

Static NAT:- One single private IP address is mapped to single public IP address. It gives access to the servers from outside. One to one mapping It gives two way accesses. Users from inside can access outside. Outside users can also access inside.

PAT (Port Address Translation) Many private ip's is mapped to one single public IP address. Advantage is both save the public IP address and security. Disadvantage is some applications will not support by PAT. Also provides only one way access. From inside to outside. Outside to inside not allowed.

Steps to configure NAT:- 1. Define private IP address range in global config mode using "access list" 2. Define public IP address pool in global config mode using "ip nat pool" 3. Map private IP range with public pool in global config mode using “ip nat inside source" 4. Apply Nat the interface mode using "ip nat inside" and "ip nat outside".

Dynamic NAT:-Example STEP 1:- Define private IP address Router(config)#access-list 1 permit STEP 2:- Define public IP address Router(config)#ip nat pool p netmask STEP 3:- Map private pool with public IP address Router(config)#ip nat inside source list 1 pool p1 STEP 4:- Apply Nat in the interface int e0=>ip nat inside int s0=>ip nat outside

PAT Example STEP 1:- Define private IP address router(config)#access-list 1 permit STEP 2:- Define public IP address router(config)#ip nat pool p netmask STEP 3:- Map private pool with public IP address or interface router(config)#ip nat inside source list 1 pool p1 overload OR router(config)#ip nat inside source list 1 interface s0 overload. STEP 4:- Apply Nat in the interface int e0=>ip nat inside int s0=>ip nat outside

Static Nat Example STEP 1:- Map private pool with public IP address or interface router(config)#ip nat inside source static STEP 2:- Apply Nat in the interface int e0=>ip nat inside int s0=>ip nat outside