What is the difference between Static NAT, Dynamic NAT, PAT?

NAT (Network Address Translation)

What is NAT : When communicating to devices in a public network, your device needs to use a source address that is a public address. NAT device enables private IPv4 to connect to the Internet. NAT enable you to change an IP address in a packet to a different address. Usually, NAT connects two networks and translates the private (inside local) addresses into public addresses (inside global) before packets are forwarded to another network. In other word Address translation allows you to translate your internal private addresses to public addresses before these packets leave your network.

What is Static NAT : In static NAT manual translation is performed by an address translation device, translating one IP address to a different one. If you have100 devices, you need to create100 static entries in the address translation table. Typically, static translation is done for inside resources that outside people want to access.

What is Dynamic NAT : Dynamic NAT is used when inside use wants to access external resource. When an inside user sends traffic through the address translation device, say a router, it examines the source IP address and compares it to the internal local address pool. If it finds a match, then it determines which inside global address pool it should use for the translation

 

What is PAT (Port Address Translation) : With PAT, all devices that go through the address translation device have the same global IP address assigned to them, so the source TCP or UDP port numbers are used to differentiate the different connections. If two devices have the same source port number, the translation device changes one of them to ensure uniqueness. Major difference between NAT and PAT is In NAT Only IP addresses are translated (not port numbers).

Network address translation is a method of mapping of private IP address to into public IP address, in order to communicate with internet. Static NAT is a type of NAT there exists one to one mapping between local and global address. Static NAT require one real public IP address for every host on your network. ( One to one mapping) Dynamic NAT is the advanced version of NAT, here you can map unregistered private IP address to registered public IP address by selecting public IP from a pool of of registered IP address. (Many to many mapping) PAT (port address translation) is also known as dynamic NAT overloading is the popular type of NAT configuration. Here you can map multiple un registered private IP address to a single registered public IP address. By PAT you will get the provision for connecting thousands of hosts to internet by using only one registered public IP address. (Many to one mapping)

Static ---------> map single internal ip address into single public ip address permanently

Dynamic -----> map internal addresses into a pool of public IP addresses. Offer or assigned IP address on the bases of first come, first get bases. Wait for next available IP address when all Public IP addresses is in use.

PAT.--------------> map internal IP addresses into single Public IP address with different internal assign port with each request. 

Static Nat :  is designed to allow one-to-one mapping between local and global addresses 

 

Dynamic Nat : designed to map an unregisterd ip address to a registred ip address from out of a pool of registred addresses 

 

Pat : is designed to map multiple unregistred ip addresse to a single registred ip address (many-to-one) and it is the most popular type

Network Address Translator(NAT)

Port Address Translator(PAT)

 

Static NAT --one public address---one private address( one to one)

 

Dynamic NAT ---group of public address -------group of private addresss(many to many)

cmd:ip nat

 

PAT----------one public address----group of private address (one to many)