The original intention for NAT was to slow the depletion of available IP address space by allowing many private IP addresses to be represented by some smaller number of public IP addresses.
NAT really decreases the overwhelming amount of public IP addresses required in your networking environment. And NAT comes in really handy when two companies that have duplicate internal addressing schemes merge.
|Conserves legally registered addresses.||Translation introduces switching path delays.|
|Reduces address overlap occurrence.||Loss of end-to-end IP traceability.|
|Increases flexibility when connecting Internet.||Certain applications will not function with to NAT enabled.|
|Eliminates address renumbering as network changes.|
Types of Network Address Translation
Three types of NAT:
The names we use to describe the addresses used with NAT are simple. Addresses used after NAT translations are called global addresses. These are usually the public addresses used on the Internet, but remember, you don’t need public addresses if you aren’t going on the Internet. Local addresses are the ones we use before NAT translation. So, the inside local address is actually the private address of the sending host that’s trying to get to the Internet, while the outside local address is the address of the destination host. The latter is usually a public address (web address, mail server, etc.) and is how the packet begins its journey. After translation, the inside local address is then called the inside global address and the outside global address then becomes the name of the destination host.
Static NAT Configuration
Dynamic NAT Configuration
PAT (Overloading) Configuration
Simple Verification of NAT
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