Quick Reference Guide

Reference Guide for the Model RT338 ISDN Router
1-12 Introduction
NETGEAR strongly advises that all hosts on a LAN segment use the same netmask for the
following reasons:
• Hosts recognize local IP broadcast packets
When a device broadcasts to its segment neighbors, it uses a destination address of the local
network address with all ones for the host address. In order for this scheme to work, all
devices on the segment must agree on which bits comprise the host address.
• Local routers or bridges can determine which addresses are local or remote
Private IP Addresses
If your networks are isolated from the Internet (for example, only between your two branch
offices), you can assign any IP addresses to the hosts without problems. However, the IANA has
reserved the following three blocks of IP addresses specifically for private networks:
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
NETGEAR recommends that you choose your private network number from this range.
The DHCP server of the Model RT338 router is preconfigured to automatically assign private
addresses.
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.
255.255.255.128 /25
255.255.255.192 /26
255.255.255.224 /27
255.255.255.240 /28
255.255.255.248 /29
255.255.255.252 /30
255.255.255.254 /31
255.255.255.255 /32
Table 1-3. Netmask Formats