ATL Telecom AM30 - Manual (Page 79)

ATL Telecom User Guide
AM30
7
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:
fStatically: If your ISP provides you with their DNS
server addresses, you can assign them to each PC by
modifying the PCs' IP properties.
fDynamically from a DHCP pool: You can configure
the DHCP Server feature on the ADSL/Ethernet router
and create an address pool that specifies the DNS
addresses to be distributed to the PCs. Refer to
Chapter 0, “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/Ethernet
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.