What is NAT?
Network Address Translation (NAT) allows a host that does not have a registered IP address to communicate with other hosts on the Internet. NAT has gained such wide-spread acceptance that the majority of enterprise networks today use private IP addresses for most hosts on their network and use a small block of public IP addresses, with NAT translating between the two.
Purpose of NAT?
NAT is a feature that allows the internal network of an organization to appear to be using a different IP address space from the outside than what it is actually using. Thus, NAT allows an organization to use private IP addresses that are not globally routable and yet connect to the Internet by translating those private addresses into globally routable addresses.
Types of NAT
In general, NAT is configured on a Cisco router that connects only two networks, and translates the inside local (private) addresses from the internal network into inside global (public) addresses. In most common scenarios the outside addresses are not translated so outside global and outside local addresses are the same. You can configure NAT in a way that it will advertise only a single address for your entire network to the outside world. Doing this effectively hides the addresses in your internal network from the hostile environment of the Internet. Thus, giving you some additional security and peace of mind as network administrator.
NAT has the following types:
Dyanamic NAT LAB
NAT overload
Network Address Translation (NAT) allows a host that does not have a registered IP address to communicate with other hosts on the Internet. NAT has gained such wide-spread acceptance that the majority of enterprise networks today use private IP addresses for most hosts on their network and use a small block of public IP addresses, with NAT translating between the two.
Purpose of NAT?
NAT is a feature that allows the internal network of an organization to appear to be using a different IP address space from the outside than what it is actually using. Thus, NAT allows an organization to use private IP addresses that are not globally routable and yet connect to the Internet by translating those private addresses into globally routable addresses.
Types of NAT
In general, NAT is configured on a Cisco router that connects only two networks, and translates the inside local (private) addresses from the internal network into inside global (public) addresses. In most common scenarios the outside addresses are not translated so outside global and outside local addresses are the same. You can configure NAT in a way that it will advertise only a single address for your entire network to the outside world. Doing this effectively hides the addresses in your internal network from the hostile environment of the Internet. Thus, giving you some additional security and peace of mind as network administrator.
NAT has the following types:
- Static NAT: Static NAT performs static address translation allowing one-to-one mapping between local and global addresses. But you should keep in mind that static NAT requires you to have one registered public IP address for every host on your network. As such static NAT has no benefit in terms of IP address conservation. Nevertheless, static NAT is important for the sake of understanding NAT.
- Dynamic NAT: Dynamic NAT performs dynamic address translation mapping unregistered private IP addresses to registered public IP addresses from a pool of available registered IP addresses. You don’t have to statically configure your router to map an inside to an outside address as you would using static NAT. But yet you do have to have enough registered public IP addresses for everyone who’s going to communicate to the Internet. Even dynamic NAT does not help with the issue of IP address conservation.
- NAT Overload: NAT overload performs an overload mapping multiple unregistered private IP addresses to a single registered public IP address. It is a many-to-one mapping between private and public addresses and is accomplished using different port numbers. This method is also known as Port Address Translation (PAT). By using PAT or NAT overload, hundreds or even thousands of users can be connected to the Internet using only one real global IP address. This is the most popular NAT type which basically is a form of dynamic map but with multiple unregistered IP addresses mapped to a single registered IP address. Dynamic NAT is one-to-one while NAT Overload or PAT is many-to-one though both forms do the mapping dynamically. NAT Overload is the type of NAT that has enabled us not to run out of IP addresses on the Internet.
Dyanamic NAT LAB
NAT overload
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