BIND&DNS Notes

What is DNS (Domain Name System)?

• a hierarchical, distributed database
• for mapping Internet host names to IP addresses and vice versa
• provides mail routing information

What are the components in the DNS?

• DNS Clients
• resolver library
• DNS server

DNS clients (e.g. Web browser is one of those) look up information in the DNS by calling a resolver library, which sends queries to one or more name servers and interprets the response.

• Domains and Domain Names
• Zones
• Recursive and iterative queries (with diagram)

DNS Servers

Authoritative Name Servers

A name server which contains the complete data for a zone.

• The primary master DNS server: maintains the master copy of the zone data
• Slave DNS servers: (aka secondary servers) load the zone contents from another server using a replication process known as zone transfer.

Non-authoritative Name Servers

• Caching Name Server, or recursive name server

A name server which performs recursive lookups for local clients. Recursive name servers normally cache the results of the lookups they perform to improve performance.

• Forwarder

Sometimes a caching name server may not perform the recursive lookup all by itself. It can forward some or all of the queries to another caching name server, commonly referred to as a forwarder.

BIND Configuration File

Caching ONLY name server

Minimal Configuration

acl intnet { 192.168.99.0/24; 172.16.0.0/16; };
options {
        directory "/var/named";
        allow-query { intnet; };
};

zone "." {
         type hint;
         file "named.cache";
};

Authoritative Primary Name Server

Minimal Configuration

options {
        directory "/var/named";
        allow-query { any; };
        recursion no;
};

zone "ops335.com" {
         type master;
         file "ops335.com.db";
         notify yes;

         allow-transfer {
             192.168.99.54;
         };
};

Authoritative Secondary Name Server

Minimal Configuration

options {
        directory "/var/named";
        allow-query { any; };
        recursion no;
};

zone "ops335.com" {
         type slave;
         file "ops335.com.bk";
         masters { 192.168.99.53; };
};

Mix-mode Name Server

Minimal Configuration

acl intnet { 192.168.99.0/24; 172.16.0.0/16; };
options {
        directory "/var/named";
        allow-query { intnet; };
};

zone "." {
         type hint;
         file "named.cache";
};
zone "ops335.com" {
         type slave;
         file "ops335.com.bk";
         masters { 192.168.99.53; };

Root Zone and Root Name Server

• ftp://ftp.rs.internic.net/domain/

Root Name Servers

• named.cache or
• named.root

Root Zone

• root.zone and
• root.zone.gz (gzip of root.zone)