Tuesday, May 17, 2011

DNS cofiguration

Domain Name System (DNS) provides the means by which the name of a website  is converted to an IP address. This is important as it is the IP address of a web site’s server, not the website’s name, that is used in routing traffic over the Internet.
BIND is an acronym for the “Berkeley Internet Name Domain” project which maintains the DNS related software suite that runs under Linux. The most well known program in BIND is “named”, the daemon that responds to DNS queries from remote machines.
A DNS client doesn’t store DNS information; it always has to refer to a DNS server to get it.The only DNS configuration file for a DNS client is the /etc/resolv.conf file which defines the IP address of the DNS server it should use. You shouldn’t need to configure any other files.
DNS servers are the servers that provide the definitive information for your DNS domain such as
the names of servers and websites in it.
There are thirteen “root” (super duper) authoritative DNS servers which all DNS servers query first. These servers know all the authoritative DNS servers for all the main domains such as .com”, “.net” etc. These servers keep track of all the sub domains beneath them. When you register a domain such as “my-site.com” you are actually inserting a record on the “.com” DNS servers that points to the authoritative DNS servers for your domain.
Packages : Bind*  ,  Caching*
Main Configuration file :  /etc/named/named.conf                 This is the main configuration file to be edited to tell where the farward and reverse lookup zones are present.
Other configuration files :       /var/named/localhost.zone     and /var/named/named.local                                                              These are the farward lookup and reverse lookup zones to be edited
Service/Daemon : named
The file /etc/resolv.conf is to be edited by giving the DNS setrver IP’s and Names.
To Check :     # dig
# dig -x < ip address>
ttl  : Time to Live
SOA : State of Authority
NS: Name Server
A : Address
@ : domain
PTR : Pointer
CNAME : Canonical name or Alias Name
MX : Mail Exchange
IN : Internet
Testing the clients:
Using nslookup to test client behaviour is obvious.