ZyXEL nbg-5715 Guia Do Utilizador

Appendix C IP Addresses and Subnetting

NBG5715 User’s Guide

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. 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 NBG5715. 

Once you have decided on the network number, pick an IP address for your NBG5715 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 NBG5715 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 NBG5715 unless you are instructed to do otherwise.

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.

13

255.255.255.248 (/29)

8192

6

14

255.255.255.252 (/30)

16384

2

15

255.255.255.254 (/31)

32768

1

16-bit Network Number Subnet Planning (continued)