Configurar servidor DNS

Fichero /etc/bind/named.conf

NOTA: En algunas distribuciones y en versiones antiguas de BIND el fichero se encuentra en /etc/named.conf

Este fichero es el fichero principal de configuración de bind. En su versión para Debian, este fichero no lo tendriamos que modificar nunca ya que solo tiene /etc/bind/named.conf.options y las zonas por defecto (que se supone que nunca se han de tocar) y delega las opciones y la creación de zonas propias a los ficheros /etc/bind/named.conf.local respectivamente.

$ cat /etc/bind/named.conf
................................................

include "/etc/bind/named.conf.options";

// prime the server with knowledge of the root servers
zone "." {
        type hint;
        file "/etc/bind/db.root";
};

// be authoritative for the localhost forward and reverse zones, and for
// broadcast zones as per RFC 1912

zone "localhost" {
        type master;
        file "/etc/bind/db.local";
};

zone "127.in-addr.arpa" {
        type master;
        file "/etc/bind/db.127";
};

zone "0.in-addr.arpa" {
        type master;
        file "/etc/bind/db.0";
};

zone "255.in-addr.arpa" {
        type master;
        file "/etc/bind/db.255";
};

....................

include "/etc/bind/named.conf.local";

El mayor recurso para conocer todas las opciónes de fichero named.conf es el manual de Linux.

• Manual: man named.conf (esta en ingles)
  
  

Fichero /etc/bind/named.conf.options

$ cat /etc/bind/named.conf.options 
 options {
       directory "/var/cache/bind";
 
       // If there is a firewall between you and nameservers you want
       // to talk to, you might need to uncomment the query-source
       // directive below.  Previous versions of BIND always asked
       // questions using port 53, but BIND 8.1 and later use an unprivileged
       // port by default.
 
       // query-source address * port 53;
 
       // If your ISP provided one or more IP addresses for stable 
       // nameservers, you probably want to use them as forwarders.  
       // Uncomment the following block, and insert the addresses replacing 
       // the all-0's placeholder.
 
       // forwarders {
       //      0.0.0.0;
       // };
 
       auth-nxdomain no;    # conform to RFC1035
 
       // By default, name servers should only perform recursive domain
       // lookups for their direct clients.  If recursion is left open
       // to the entire Internet, your name server could be used to
       // perform distributed denial of service attacks against other
       // innocent computers.  For more information on DDoS recursion:
       // http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2006-0987
 
       allow-recursion { localnets; };
 
       // If you have DNS clients on other subnets outside of your
       // server's "localnets", you can explicitly add their networks
       // without opening up your server to the Internet at large:
       // allow-recursion { localnets; 192.168.0.0/24; };
  
       // If your name server is only listening on 127.0.0.1, consider:
       // allow-recursion { 127.0.0.1; }; 

Normalmente lo que siempre se modifica de este fichero es el apartado forwarders y es donde se especifican los servidores DNS de nuestro proveedor de servicios.

Fichero /etc/bind/named.conf.local

En este fichero hemos de configurar las zonas de las que queremos que el servidor DNS se encargue. Un ejemplo puede ser:

zone "0.168.192.in-addr.arpa" {
  type master;
  file "/var/lib/named/192.168.0.rev";
  };
zone "1.168.192.in-addr.arpa" {
  type master;
  file "/var/lib/named/192.168.1.rev";
  };
zone "iesdeltebre.net" {
  type master;
  file "/var/lib/named/iesdeltebre.net.hosts";
  };
zone "intracentre" {
  type master;
  file "/var/lib/named/intracentre.hosts";
  };

Aquí se configuran dos redes privadas de clase C (192.168.0.0/24 y 192.168.1.0/24). Los nombres de las zonas de resolución inversas en cada caso son iesdeltebre.net y intracentre.

$ttl 38400                                                    
0.168.192.in-addr.arpa. IN   SOA   s-207. ocastell (          
             2003062504                                                     
             10800                                                          
             3600                                                           
             604800                                                         
             38400 )                                                              
2.0.168.192.in-addr.arpa.  IN   PTR    s-207.iesdeltebre.net. 
2.0.168.192.in-addr.arpa.  IN   PTR    iesdeltebre.net.

$ttl 38400
iesdeltebre.net.  IN     SOA   s-207. ocastell (
              2003062502
              10800
              3600  
              604800
              38400 )
iesdeltebre.net.       IN NS     s-207.
0.168.192.in-addr.arpa.    IN   NS    s-207.
s-207.iesdeltebre.net. IN    A      192.168.0.2
iesdeltebre.net.        IN CNAME s-207
www.iesdeltebre.net.    IN CNAME s-20