These different categories are then used to define different types of address depending on location of the address and how it is being “seen”. O utside indicates traffic that is coming from an external network that is outside the organizational network. Inside indicates traffic that is coming from within the organizational network. In typical NAT configurations, interfaces are placed into one of two categories (or locations): inside or outside. There are a couple of main concepts that also must be reviewed and understood before configuring NAT: This is not a complete list of every possible way that NAT can be configured but simply a list of the most common ways that it is used in modern networks. In this scenario, commonly, a single public address is translated into one of several internal addresses in a round robin fashion. This is very common, as many highly used servers are not really a single machine but a bank of several machines that utilize load balancing. When simple TCP load sharing is required across many IP hosts:.This is often done when a company is transitioning their IP addressing plan common scenarios include when expanding (and the IP addressing plan was not built sufficiently when the initial addresses were assigned) and when a company is merging with another with potential overlapping addresses. Translation of addresses when transitioning internal addresses from one address range into another (this is common when the organization of addresses within a company is being changed):.This is one of the most common uses of NAT today almost every household that has a “router” to access the Internet is using NAT on this device to translate between internal private address and public Internet addresses. Translation of non-unique addresses into unique addresses when accessing the Internet:.This section reviews these different concepts and begins with an understanding of how NAT can be used. There are a number of different concepts that must be explained in order to really get a good understanding of how NAT operates, which ultimately makes the configuration of NAT increasingly simple.
This article looks at some of the basic concepts that are used when configuring NAT and reviews the configuration steps required to get NAT working. At its most basic, NAT enables the ability to translate one set of addresses to another this enables traffic coming from a specific host to appear as though it is coming from another and do it transparently. The use of Network Address Translation (NAT) has been widespread for a number of years this is because it is able to solve a number of problems with the same relatively simple configuration.