Tuesday, January 13, 2009

DNS query Forwarding

In Domain Name System (DNS), DNS server forwards DNS queries for resolving external DNS names. DNS query forwarder, name resolution for names outside your network can be easily managed.

The following illustrates the DNS query forwarding

A DNS server that is used as a DNS query forwarder behaves as follows:

  1. After receiving DNS query, DNS server attempts to resolve this query by using the domain zones that the server it hosts and by using its cache.
  2. If the step 1 fails then the DNS server forwards the DNS query to the DNS server that acts as a DNS query forwarder.
  3. If above fails, then DNS server attempts to use its root hints of DNS query Domain Name to resolve it.

Following are the advantages to use DNS server forwarding in an organization.
1 Since DNS server forwarder is responsible for handling external traffic, DNS server can be hided from exposure to external network.
2. A DNS server forwarder caches external DNS information so that the response time for DNS clients is low.

Note: DNS server on a network that forwards DNS queries according to the DNS domain name in the query is called conditional DNS query forwarder. For example, A DNS server can be configured to forward all the DNS queries for domain names ending with dns-info.blogspot.com to the IP address of a specific DNS server or to the IP addresses of multiple DNS servers. Windows 2003 and windows 2008 supports conditional forwarding.


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