Bind DNS server: redirect only subdomain

Question

We've some domain (mydom.tld) and in the svn subdomain we have the Subversion server.

This server resides in the main office, and must be accessed inside this office as well as outside it.

So, now we have to edit the /etc/hosts file each time we enter the office, and re-edit when we go outside to make it work.

I've configured the DNS server (bind9 under Ubuntu) so we can use it as I described above, but the problem is that it manages the whole mydom.tld domain, when I only want it to manage the subdomain.

Desired behavior:

• mydom.tld -> no answer
• asdf.mydom.tld -> no answer
• svn.mydom.tld -> 192.168.1.X

Can someone give a solution based on the file /etc/bind/named.conf.local and similar ones?

Answer 1

You can use the view feature of bind with this named.conf :

view "internal" {
 match-clients { 192.168.1.0/24; }; // your network
  recursion yes;
  // required zone for recursive queries
  zone "." {
   type hint;
   file "root.servers";
  };
  zone "sub.mydom.tld" {
   type master;
   // private zone file including local hosts
   file "view/master.sub.mydom.tld.internal";
  };
  // required local host domain
  zone "localhost" in{
   type master;
   file "master.localhost";
   allow-update{none;};
  };
  // localhost reverse map
  zone "0.0.127.in-addr.arpa" in{
   type master;
   file "localhost.rev";
   allow-update{none;};
  };
}; // end view

// external hosts view
view "external" {
 match-clients {"any"; }; // all other hosts
  // recursion not supported
  recursion no;
 zone "mydom.tld" {
   type master;
     // only public hosts
   file "view/master.example.com.external";
  };
}; // end view

Answer 2

Getting no answer for mydom.tld is easy. I suspect what you want is for it to give the correct answer.

i.e.

Outside the office you get this:

• mydom.tld -> 10.0.0.1
• asdf.mydom.tld -> NXDOMAIN
• svn.mydom.tld -> 10.0.0.2

Inside, you get this:

• mydom.tld -> 10.0.0.1
• asdf.mydom.tld -> NXDOMAIN
• svn.mydom.tld -> 192.168.1.1

The easiest way I can see is to copy your production Bind config down to your Office Bind server and edit just that one entry. You could set this up in a daily cron job so that any changes to production are reflected in the office 24 hours later. (Details of this are up to you - hourly cron job, SVN checkout, etc.)

If you aren't running Bind in production or you are using a third-party service such as your registrar's DNS service, then you could use a zone transfer instead. (AXFR)