ZyXEL Communications Prestige 642R Series - Manual (Page 45)

Prestige 642R Series ADSL Router
3-2 Internet Access
3.3 TCP/IP Parameters
3.3.1 IP Address and Subnet Mask
Like houses on a street that share a common street name, the machines on a LAN share one common network
number.
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 (ignoring the trailing
zero) and you must enable the Single User Account feature of the Prestige. 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.
The subnet mask specifies the network number portion of an IP address. Your Prestige 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 Prestige unless you are instructed to do otherwise.
3.3.2 Private IP Addresses
Every machine on the Internet must have a unique 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:
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
You can obtain your IP address from the IANA, from an ISP, or it can be assigned from 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.
Note: Regardless of your particular situation, do not create an arbitrary IP address;
always follow the guidelines above. For more information on address assignment,
please refer to RFC 1597, Address Allocation for Private Internets and RFC 1466,
Guidelines for Management of IP Address Space.