ZyXEL Communications P-661H-61, Manual

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Appendix A IP Addresses and Subnetting
P-661HNU-Fx User’s Guide
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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 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.
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.
IP Address Conflicts
Each device on a network must have a unique IP address. Devices with duplicate
IP addresses on the same network will not be able to access the Internet or other
resources. The devices may also be unreachable through the network.
Conflicting Computer IP Addresses Example
More than one device can not use the same IP address. In the following example
computer A has a static (or fixed) IP address that is the same as the IP address
that a DHCP server assigns to computer B which is a DHCP client. Neither can
access the Internet. This problem can be solved by assigning a different static IP