Telindus 1031, User And Reference Manual

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Telindus 1031 Router Chapter 7
User manual Configuring the router
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7.4.1 Introducing NAT and PAT
What is NAT and PAT?
Network Address Translation (NAT) and Port Address Translation (PAT) are used to translate private IP
addresses into official IP addresses. This is also known as IP masquerading.
If you use the Telindus 1031 Router to have a permanent connection to the Internet, you may need NAT
and/or PAT.
Why use NAT and PAT?
Each device connected to the Internet must have an official (i.e. unique) IP address. The success of the
Internet has caused a lack of these official IP addresses. As a result, your Internet Service Provider (ISP)
may offer you only one or a small number of official IP addresses.
If the number of IP devices on your local network is larger than the number of official IP addresses, you
can assign test or private IP addresses to your local network. In that case, you have to configure your
Telindus 1031 Router to translate IP addresses using NAT or PAT.
Even when there are sufficient official IP addresses available, you may still choose to use NAT e.g. for
preserving previously assigned test addresses to all the devices on your local network.
Private IP address range
The international authority IANA assigns the official (also called global) IP addresses. It has also defined
3 ranges of IP addresses for private use. This means that you can use these addresses without regis-
tration on your internal network, as long as you are not connected to the Internet.
You can define (sub-)networks in these ranges for your private IP addresses .
Private IP address range Remarks
10.0.0.0 - 10.255.255.255 1 class A network
172.16.0.0 - 172.31.255.255 16 class B networks
192.168.0.0 - 192.168.255.255 256 class C networks