User's Manual

9 Configuring DNS Server Addresses

About DNS

Domain Name System (DNS) servers map the user-friendly domain

names that users type into their Web browsers (e.g., "yahoo.com")

to the equivalent numerical IP addresses that are used for Internet

routing.

When a PC user types a domain name into a browser, the PC must

first send a request to a DNS server to obtain the equivalent IP

address. The DNS server will attempt to look up the domain name

in its own database, and will communicate with higher-level DNS

servers when the name cannot be found locally. When the address

is found, it is sent back to the requesting PC and is referenced in IP

packets for the remainder of the communication.

Assigning DNS Addresses

Multiple DNS addresses are useful to provide alternatives when one

of the servers is down or is encountering heavy traffic. ISPs typically

provide primary and secondary DNS addresses, and may provide

additional addresses. Your LAN PCs learn these DNS addresses in

one of the following ways:

 Statically: If your ISP provides you with their DNS server

addresses, you can assign them to each PC by modifying

the PCs' IP properties.

 Dynamically from a DHCP pool: You can configure the

DHCP Server feature on the ADSL Router and create an

address pool that specify the DNS addresses to be

distributed to the PCs. Refer to Chapter 7, “Configuring

DHCP Server” on page 53 for instructions on creating

DHCP address pools.

In either case, you can specify the actual addresses of the ISP's

DNS servers (on the PC or in the DHCP pool), or you can specify

the address of the LAN port on the ADSL Router (e.g.,

192.168.1.1). When you specify the LAN port IP address, the

device performs DNS relay, as described in the following section.

Note

If you specify the actual DNS addresses on the PCs or in the

DHCP pool, the DNS relay feature is not used.