Dhcp (Dynamic Host Configuration Protocol) Configuration - ZyXEL Communications Prestige 100L User Manual

Prestige 100L IDSL Router

3.1.5 DHCP (Dynamic Host Configuration Protocol) Configuration

DHCP allows the individual clients (workstations) to obtain the TCP/IP configuration at start-up from a
server. Unless you are instructed by your ISP, leave the DHCP at the Server default value. You can
configure the Prestige as a DHCP server or disable it. When configured as a server, the Prestige provides the
TCP/IP configuration for the clients.
IP Pool Setup
The Prestige is pre-configured with a pool of 32 IP addresses starting from 192.168.1.33 to 192.168.1.64.
This configuration leaves 31 IP addresses (excluding the Prestige itself) in the lower range for other server
machines, e.g., server for mail, FTP, telnet, web, etc., that you may have.
DNS (Domain Name System) Server Address
DNS is for mapping a domain name to its corresponding IP address and vice versa, e.g., the IP address of
www.zyxel.com is 204.217.0.2. The DNS server is extremely important because without it, you must know
the IP address of a machine before you can access it.
There are two ways that an ISP disseminates the DNS server addresses. The first is for an ISP to tell a
customer the DNS server addresses, usually in the form of an information sheet, when you sign up. If your
ISP does give you the DNS server addresses, enter them in the DNS Server fields in DHCP Setup. The
second is to leave this field blank, i.e., 0.0.0.0, – in this case the Prestige acts as a DNS proxy.
IP Subnet Mask
A subnet mask is a 32-bit quantity that, when logically ANDed with an IP address, yields the network
number. For instance, the subnet masks for Class A, B, and C without subnetting are 255.0.0.0, 255.255.0.0,
and 255.255.255.0, respectively. To create more network numbers, you shift some bits from the host ID to
the network ID. For instance, to partition a Class C network number 192.68.135.0 into two, you shift 1 bit
from the host ID to the network ID. Thus the new subnet mask is 255.255.255.128; the first subnet have a
network number of 192.68.135.0 with hosts 192.68.135.1 to 192.68.135.126 and the second subnet have a
network number of 192.68.135.128 with hosts 192.68.135.129 to 192.68.135.254. It is recommended that
you use the same subnet mask for all physical networks that share an IP network number. The following table
lists the additional subnet mask bits in dot decimal notations. To use the following table, write down the
original subnet mask and substitute the higher order "0"s with the dot decimal of the additional subnet bits.
For instance, to partition your Class C network 204.247.203.0 with subnet mask 255.255.255.0 into 16
subnets (4 bits), the new subnet mask becomes 255.255.255.240.
Internet Access 3-3