Private Ip Addresses; Table 5-2 Private Ip Address Ranges - ZyXEL Communications ZyWALL 10/10 User Manual

Where you obtain your network number depends on your particular situation. If the ISP or your network
administrator assigns you a block of registered IP addresses, follow their instructions in selecting the IP
addresses and the subnet mask.
If the ISP did not explicitly give you an IP network number, then most likely you have a single user account
and the ISP will assign you a dynamic IP address when the connection is established. If this is the case, it is
recommended that you select a network number from 192.168.0.0 to 192.168.255.0 and you must enable the
Network Address Translation (NAT) feature of the ZyWALL. The Internet Assigned Number Authority
(IANA) reserved this block of addresses specifically for private use; please do not use any other number
unless you are told otherwise. Let's say you select 192.168.1.0 as the network number; which covers 254
individual addresses, from 192.168.1.1 to 192.168.1.254 (zero and 255 are reserved). In other words, the first
three numbers specify the network number while the last number identifies an individual workstation on that
network.
Once you have decided on the network number, pick an IP address that is easy to remember, e.g.,
192.168.1.1, for your ZyWALL, but make sure that no other device on your network is using that IP.
The subnet mask specifies the network number portion of an IP address. Your ZyWALL will compute the
subnet mask automatically based on the IP address that you entered. You don't need to change the subnet
mask computed by the ZyWALL unless you are instructed to do otherwise.

5.3.4 Private IP Addresses

Every computer on the Internet must have a unique IP address. If your networks are isolated from the
Internet, e.g., only between your two branch offices, you can assign any IP addresses to the hosts without
problems. However, the Internet Assigned Numbers Authority (IANA) has reserved the following three
blocks of IP addresses specifically for private networks:
You can obtain your IP address from the IANA, from an ISP or have it assigned by a private network. If you
belong to a small organization and your Internet access is through an ISP, the ISP can provide you with the
Internet addresses for your local networks. On the other hand, if you are part of a much larger organization,
you should consult your network administrator for the appropriate IP addresses.
LAN Setup

Table 5-2 Private IP Address Ranges

10.0.0.0 — 10.255.255.255
172.16.0.0 — 172.31.255.255
192.168.0.0 — 192.168.255.255
ZyWALL 10/10 II/50 Internet Security Gateway
5-3