Networking - Networking Basics - Discussion

Network Address Translation (NAT) and Port Address Translation (PAT) both map IP addresses on an internal network to IP addresses on an external network. Which method of address translation you use depends on the types of networks that you are translating and the number of available IP addresses that you have.

If you are connecting a site to the 10.10.10.0 network to a site in the 10.10.20.0 network, you could use NAT to translate 10.10.10.0 IP addresses to available 10.10.20.0 IP addresses so that hosts on the 10.10.10.0 network can access data and use network resources on the 10.10.20.0 network. However, for this scenario to work, you must have an address pool that contains enough available IP addresses on the 10.10.20.0 network to accommodate every host on the 10.10.10.0 network, because NAT requires a one-to-one relationship when translating IP addresses.

PAT attempts to use the original source port number of the internal host to form a unique, registered IP address and port number combination. For example, two hosts that have been assigned the IP addresses 10.10.10.100 and 10.10.10.101, respectively, could send traffic to and receive traffic from the Internet by using the single public IP address 123.45.67.89. If that port number is already allocated, PAT searches for an available alternate source port number. Therefore, the host at IP address 10.10.10.100 could access the Internet by using the public IP address and source port combination of 123.45.67.89:10000. Meanwhile, the host at IP address 10.10.10.101 could access the Internet by using the IP address and source port combination of 123.45.67.89:10001.

Static NAT (Network Address Translation) - Static NAT (Network Address Translation) is a one-to-one mapping of a private IP address to a public IP address. Static NAT (Network Address Translation) is useful when a network device inside a private network needs to be accessible from the internet.

Dynamic NAT (Network Address Translation) - Dynamic NAT can be defined as a mapping of a private IP address to a public IP address from a group of public IP addresses called as NAT pool. Dynamic NAT establishes a one-to-one mapping between a private IP address to a public IP address. Here the public IP address is taken from the pool of IP addresses configured on the end NAT router. The public to private mapping may vary based on the available public IP address in NAT pool.

PAT (Port Address Translation) - Port Address Translation (PAT) is another type of dynamic NAT which can map multiple private IP addresses to a single public IP address by using a technology known as Port Address Translation.

Here when a client from inside network communicate to a host on the internet, the router changes the source port (TCP or UDP) number with another port number. These port mappings are kept in a table. When the router receives from the internet, it will refer the table which keeps the port mappings and forward the data packet to the original sender.

Basic For NAT : With the explosion of the Internet and the increase in home networks and business networks, the number of available IP addresses is simply not enough. This is where NAT comes to the rescue. Network Address Translation allows a single device, such as a router, to act as an agent between the Internet (or "public network") and a local (or "private") network. This means that only a single, unique IP address is required to represent an entire group of computers.

NAT is used by a device and do mapping of an unregistered IP address to a registered IP address on a one-to-one basis.

NAT that maps multiple unregistered IP addresses to a single registered IP address by using different ports. This is known also as PAT (Port Address Translation).

NAT is a protocol that translates inside addresses (private address) into global inside address (public ips). Its developed to hold the shortage of IPv4. It allow to have thousands of hosts with private ip address to be translated in public addresses.

PAT, is the same thing as NAT. The difference is, instead of translating ip's, PAT translate into ports. Its ensure a company that have ONLY one public ip address to communicate with external hosts.

Summarizing:

- If we have like 200 hosts in a company and have more than 2 addresses, we use NAT;

- If we have like 200 hosts in a company and have only 1 public address, we use NAT and PAT (if we have many internal hosts to a single public address it can cause problems).

Even I didnt get the difference between NAT and PAT. I know individual definitions but as far as difference is concerned...not clear yet. From Configuration point of view the difference while applying at router is : PAT uses an additional word i.e. overload.

Ex: ip nat inside Source list [access list number] pool [pool name] overload..........in PAT.

For NAT the command remains same but without overload.

NAT:

Short for Network Address Translation, an Internet standard that enables a local-area network (LAN) to use one set of IP addresses for internal traffic and a second set of addresses for external traffic.

PAT:

Short for port address translation, a type of network address translation. During PAT, each computer on LAN is translated to the same IP address, but with a different port number assignment.

NAT is static network address translation that is used to convert one IP private of local translate into public one ip address private allow many users to connect to the global internet.

PAT:-is dynamic port address translation that is used to convert multiple ip private to public IP address.

Multiple IP address privates allow many users to connect to the global internet.

Ex. When 2 host access google.com then the IP address of host are 192.168.1.1 port no is 80 also 192.168.1.2 p.no 80 when the router receive packet from google.com.

It will change port number for ex. Public IP is 21.10.1.1 P.81 for 192.168.1.1 P.No 80 and 21.10.1.1 P.No 82 for 192.168.1.2 P.No 80. In router there will be change in port addr of host that is called PAT.

PAT (Port Address Translation) includes ports in addition to IP addresses.

Many-to-one translation. Maps multiple IP addresses to 1 or a few IP addresses. Unique source port number identifies each session. Conserves registered IP addresses.

Also called NAPT (Network Address Port Translation) in IETF (Internet Engineering Task Force) documents.

PAT-PORT ADDRESS TRANSLATION; NAT-NETWORK ADDRESS TRANSLATION. In my sense both are similar both share one ip address. In simple words the PAT is the NAT overloading where it uses one ip address for all clients to multiple ports. Whereas as a standard NAT is one-to one ip address relation.