ZyXEL Communications 480 - Manual (Page 50)

Prestige 480 ISDN Router
3-4 Internet Access
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 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.
Relay Server Address
When the DHCP is set to Relay, the Prestige will request IP addresses from a real DHCP server
and relay the address to the workstation making the request.