ZyXEL Communications P-660N-T1A, User Manual

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Appendix B IP Addresses and Subnetting
P-660N-T1A User’s Guide
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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. 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. You must
also enable Network Address Translation (NAT) on the ZyXEL Device.
Once you have decided on the network number, pick an IP address for your ZyXEL
Device that is easy to remember (for instance, 192.168.1.1) but make sure that
no other device on your network is using that IP address.
The subnet mask specifies the network number portion of an IP address. Your
ZyXEL Device 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 ZyXEL Device unless you are instructed to do otherwise.
Private IP Addresses
Every machine on the Internet must have a unique address. If your networks are
isolated from the Internet (running only between two branch offices, for example)
you can assign 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.
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.