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 NAT2. Static NAT3. 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 mappingIt 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:-ExampleSTEP 1:-Define private IP addressRouter(config)#access-list 1 permit 10.0.0.0 0.255.255.255 STEP 2:- Define public IP addressRouter(config)#ip nat pool p1 200.1.1.1 200.1.1.100 netmask 255.255.255.0 STEP 3:-Map private pool with public IP addressRouter(config)#ip nat inside source list 1 pool p1 STEP 4:- Apply Nat in the interfaceint e0=>ip nat insideint s0=>ip nat outside

PAT Example

STEP 1:-Define private IP addressrouter(config)#access-list 1 permit 10.0.0.0 0.255.255.255 STEP 2:- Define public IP addressrouter(config)#ip nat pool p1 200.1.1.101 200.1.1.101 netmask 255.255.255.255 STEP 3:-Map private pool with public IP address or interfacerouter(config)#ip nat inside source list 1 pool p1 overloadOR 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 10.1.1.1 200.1.1.101 STEP 2:- Apply Nat in the interface int e0=>ip nat inside int s0=>ip nat outside