UNIX for Beginners Questions & Answers

Can you add multiple domains to a nameserver without creating a new IP address? I have one IP address on my machine and have configured forward and reverse zone files. Names are resolving fine.

I know I can add another domain to the named.conf file and create new forward and reverse files. what name server IP would i add to the forward file for the second domain and how is it configured in the forward file? Also I have named my reverse file with the reverse of the first 3 octets of my system IP address. I need to change that and what should i use for the reverse zone names?

Code:

named.conf:

zone "myserver.com" {
        type master;
        file "fwd.myserver.com.db";
        allow-update { none; };
};

zone "xx.xx.xxx.in-addr.arpa" {
        type master;
        file "xx.xx.xxx.db";
        allow-update { none; };
};

zone "newdomain.com" {
        type master;
        file "fwd.newdomain.com.db";
        allow-update { none; };
};


/var/named:

cat fwd.myserver.com.db

$TTL 86400
@       IN      SOA     nameserver.myserver.com.     root.myserver.com.      (
                                10030   ;Serial
                                3600    ;Refresh
                                1800    ;Retry
                                604800  ;Expiry
                                86400   ;Minimum TTL
)
; Name Server
@       IN      NS      nameserver.myserver.com.
;A Record Definitions
nameserver	IN	A	xxx.xx.xx.xx
server1        IN      A	xxx.xx.xx.xx
server2      IN	A	xxx.xx.xx.xx

How do I configure the forward zone record for the newdomain? i have used the one system IP address for the name server in the myserver.com domain.

Yes, you set can set A records on your name server to map any name to an IP address.

Or you can set up aliases to map any name to another A record.

It is usually (but not always) better to keep to a single A record for an IP address with a matching PTR record so the IP address can be used to find out the host. Other things, such as service names or alternate domain entries can be added as CNAME or alias records. If you have a service that other things connect to and use that has a logical name, then it is usual to define that as an alias. When you come to replace your servers, if the applications all use a CNAME/alias then you can edit the DNS to move the alias to point to the new server when you are happy that it is ready.


Additionally, if you have a cluster of servers, you might consider more things. For an Active/Passive cluster, you would have an A record for each server, but make every connection to the application(s) to use a separate IP address that you move to the active server, a virtual IP if you like. Consider:-

Make the 'active' server also offer the Myapp IP address and make connections point to service name Myapp

For an Active/Active cluster, you need some sort of load-balancer, but that's a whole extra topic.


What do you actually want to do with the applications offered by the server and how would you consider transferring them to a replacement later?


Robin