I covered secondary DNS configuration in Tiger (10.4) Server a while back. And while the buttons have moved around a bit, most of those instructions apply to Leopard as well. Leopard does have one fairly cool new addition worth mentioning, though: forwarders.
Generally I’m setting up secondary DNS for internal networks, and generally those internal DNS servers serve DNS only for the internal networks. Everything outside the internal network is handled by external DNS servers (or by DNS servers that sit on a network of which we are a subdomain), and our internal DNS servers need to know who those server are. These external servers are called forwarders, in DNS parlance. They are the first stop for all DNS outside your local network. And you can now set them on your secondary DNS server in the Leopard Server Admin application.
Leopard's Forwarders Pane
To get to the settings, navigate to the “Settings” tab under the DNS service. In the bottom-most pane of the window you will see a box labeled “Forwarder IP Addresses:” Click the plus sign to add a server to the list, then type in an IP address. Typically you will add two addresses, one for the primary external DNS server and one for the secondary. These will often be your ISP’s DNS servers, though if you’re on a subdomain of a larger network you’ll use the DNS servers for that network’s domain (i.e. the subdomain systemsboy.com.mail will use the DNS servers for the domain systemsboy.com). Once you’ve entered and saved the settings, restart your DNS service and you’re off to the races.
Requests for internal network resources will still be handled by your internal DNS server, but now external requests for things like “google.com” will be passed to the appropriate external DNS server. Even if your secondary has to take over DNS duties for a long period of time, you’ll still be able to properly reach the Big Bad Internet without having to use cached or stale settings.
This is a very handy addition to the DNS configuration GUI in Server Admin.
2 Comments
Hi, thanks for the post, can you provide any information on how these can be ordered?
Hi, Damian.
Forwarders are ordered in the order they’re entered in the Forwarders pane. The first entry made will be at the top of list. Subsequent entries are lower in the list. From what I can tell, the list is read top-to-bottom. So the first (top) entry in the list is consulted first, the second entry consulted second, etc. on down the list.
The forwarders are entered in a flat text file, BTW. That file is:
/etc/dns/options.conf.apple
Hope that helps.
-systemsboy