ZyXEL Communications Prestige 202 User Manual page 65

Prestige 202 ISDN Router
DNS Server Address
DNS (Domain Name System) 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, a user must know the IP address of a machine before s/he 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 s/he
signs 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.
Some ISP's choose to pass the DNS servers using the DNS server extensions of PPP IPCP (IP
Control Protocol) after the connection is up. If your ISP did not give you explicit DNS servers,
chances are the DNS servers are conveyed through IPCP negotiation. The Prestige supports the
IPCP DNS server extensions through the DNS proxy feature.
If the Primary and Secondary DNS Server fields in DHCP Setup are not specified, i.e., left as
0.0.0.0, the Prestige tells the DHCP clients that it by itself is the DNS server. When a workstation
sends a DNS query to the Prestige, the Prestige forwards the query to the real DNS server learned
through IPCP and relays the response back to the workstation.
Please note that DNS proxy works only when the ISP uses the IPCP DNS server extensions. It does
not mean you can leave the DNS servers out of the DHCP setup under all circumstances. If your
ISP gives you explicit DNS servers, make sure that you enter their IP addresses in the DHCP
Setup menu. This way, the Prestige can pass the DNS servers to the workstations and the
workstations can query the DNS server directly without the Prestige's intervention.
Example of Network Properties for LAN Servers With Fixed IP#
Choose an IP:
Netmask:
Gateway (or default route): 192.168.1.1 (Prestige LAN IP)
DNS server:
Domain:
3-4
192.168.1.2 to 192.168.1.32; 192.168.1.65 to 192.168.1.254.
255.255.255.0
192.168.1.1
(optional)
Internet Access