Network Address Translation (NAT)

Network Address Translation (NAT)

NAT translates between local network and Internet IP addresses.

All hosts that connect to the local network are assigned with local network IP addresses by the DHCP server running in the local network’s router. When this router connects to the Internet, it is assigned with one IP address from the Internet service provider’s DHCP server. All local network hosts will share this public IP address to access the Internet.

nat.png

NAT Translation Table

How do all hosts on a local network share the same public IP address? Network Address Translation (NAT) re-assigns IP addresses and port numbers and keeps track of these re-assignments using its NAT translation table.

When the router receives a packet from a local host containing a public IP address, it changes the source IP address to use its Internet IP address and changes the source port number so it knows which local host process to deliver received packets to. This re-assignment is entered into the translation table.

Each process requiring Internet access running on the local network is assigned a new IP address and port number by NAT. Each re-assignment is then entered into the NAT translation table.

nat_table.png
© 2024 Microchip Technology, Inc.
Notice: ARM and Cortex are the registered trademarks of ARM Limited in the EU and other countries.
Information contained on this site regarding device applications and the like is provided only for your convenience and may be superseded by updates. It is your responsibility to ensure that your application meets with your specifications. MICROCHIP MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL, STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION, QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS FOR PURPOSE. Microchip disclaims all liability arising from this information and its use. Use of Microchip devices in life support and/or safety applications is entirely at the buyer's risk, and the buyer agrees to defend, indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting from such use. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights.