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NAT

Network Address Translation

Translation of network addresses used in particular to share a public IP address between several private devices

TopicIT knowledge → About 1 min read

Simple definition….

The NAT allows several devices in a local network to use a single public address to access the Internet.

Technical definition….

A router or firewall rewrites packet addresses and, for port-based NAT, transport-layer ports. SNAT changes the source address, while DNAT changes the destination. Port forwarding is a common DNAT use case.

What’s the point?… ?

Save public IPv4 addresses and publish certain services in a controlled manner.

Concrete example…

For example, devices on 192.168.1.0/24 can access the Internet using one public IPv4 address through source NAT.

Common problems….

  • Redirect to the wrong internal address
  • Port already used
  • Double NAT
  • Confusion between NAT and the Rule ofGart

Note: Exact settings and behavior depend on the product, software version and network environment.

Related resources

Relevant topic IP Address a logical address that identifies an interface or equipment on a network using IP protocol Relevant topic Firewall A firewall filters network communications using security rules that allow or block traffic based on its characteris... Relevant topic Router A router forwards IP packets between networks using the destination address and a routing table. Relevant topic Network Port A logical number identifying a service or application on an IP address. Relevant topic LAN Local network connecting the equipment of a home, office or site.
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