Bay Technical Associates RM356 - Manual (Page 30)

Reference Guide for the Model RM356 Modem Router
1-12 Introduction
Regardless of your particular situation, do not create an arbitrary IP address; always follow the
guidelines explained here. For more information about address assignment, refer to RFC 1597,
Address Allocation for Private Internets, and RFC 1466, Guidelines for Management of IP
Address Space.
Single IP Address Operation Using NAT
If multiple stations on a LAN need to access the Internet simultaneously, they usually have to
obtain a range of IP addresses from the ISP. This type of Internet account is much more costly than
a single-address account typically used by a single user with a terminal adapter rather than a router.
The Model RM356 Modem Router employs a method called extended NAT. This method allows
an entire department of networked PCs to share an Internet account using only a single IP address,
which may be statically or dynamically assigned by your ISP.
The router accomplishes this address sharing by translating the internal LAN IP addresses to a
single address that is globally unique on the Internet. The internal LAN IP addresses can be either
private addresses or registered addresses. For more information about IP address translation, refer
to RFC 1631, The IP Network Address Translator (NAT).
Figure 1-3 illustrates a single IP address operation.
Figure 1-3. Single IP Address Operation Using NAT
7786EA
192.168.0.2
192.168.0.3
192.168.0.4
192.168.0.5
192.168.0.1 172.21.15.105
Private IP addresses
assigned by user
Internet
IP addresses
assigned by ISP