ZyXEL Communications ES-2108, User Manual, Page: 265 / 284

Appendix B IP Addresses and Subnetting
ES-2108 Series User’s Guide
265
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 address to computer A or setting computer A to obtain
an IP address automatically.
Figure 161 Conflicting Computer IP Addresses Example
Conflicting Router 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.
Figure 162 Conflicting Computer IP Addresses Example