DI-206 ISDN Remote Router
Network Address Port Translation (NAPT) is a subset of NAT where many local IP addresses and their TCP/UDP port numbers are translated to a single global IP address and it’s TCP/UDP port number. In this document, the term NAT will refer to both NAT and NAPT unless otherwise stated.
NAT can work in conjunction with DHCP. Thus, if both are enabled and properly configured, the DHCP server in the
How NAT Works
In the most common NAT configuration, your network uses local IP addresses that are not valid on the Internet. Internet (global) IP addresses are unique, with no two devices have the same IP address. The local IP addresses can be freely assigned to computers on your network by your network administrator (within guidelines defined later in this chapter and in Appendix B, “IP Concepts”). This can be done manually or by using DHCP. The ISDN port on the router is assigned a globally unique IP Address that IS valid on the Internet, since it will be sending and receiving data directly to the Internet and is therefore part of it. Please study the example diagram below carefully.
Single
Global
IP Address
176.220.22.1
ISDN
PortWAN
Router NAT
Translator
LAN
Port
Local IP | LAN |
192.168.100.1
192.168.100.2 192.168.100.3 192.168.100.4 192.168.100.5
Please note that in the above diagram, the Gateway IP address settings for the local PC’s needs to be set to 192.168.100.1, the LAN IP address of the router.
NAT manipulates the IP addresses in packet headers on a
51