ZyXEL nbg-5715 Guia Do Utilizador

 Appendix C IP Addresses and Subnetting

NBG5715 User’s Guide

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. 

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 address to computer A or setting computer A to obtain an IP address 
automatically.  

Conflicting Computer IP Addresses Example

Since a router connects different networks, it must have interfaces using different network 
numbers. For example, if a router is set between a LAN and the Internet (WAN), the router’s LAN 
and WAN addresses must be on different subnets. In the following example, the LAN and WAN are 
on the same subnet. The LAN computers cannot access the Internet because the router cannot 
route between networks.

Conflicting Router IP Addresses Example