web-nsupdate: A Lightweight Dynamic DNS Service

Earlier this year, I changed my residential broadband network gateway to a Linksys WRT54G running the OpenWrt Linux distribution. Back in July, I wrote about why dynamic DNS is useful to in this sort of environment, and my frustration that the nsupdate utility is so ill-suited to it.

The solution I described was to run nsupdate not on the WRT54G client, but on a remote server that has the MIPS and MBs to run it. I implemented a package called web-nsupdate that runs on the server and receives requests from the client to set its host address. Requests are performed as a simple web transaction.

For instance, after my router renews its host address, it runs:

    wget -q -O- "http://www.example.com/web-nsupdate.php?host=home-router.example.com&addr=111.222.333.444&key=xxxxxxxx"

(Sorry for long line above. Click on switch to printable format at the very bottom of the page to see better.)

This tells the web-nsupdate service running on www.example.com to set the host address of home-router.example.com. The key value is a secret password that authorizes the update.

The web-nsupdate package is posted here.

It is, unfortunately, not all that easy to get going. It isn't that tough to setup web-nsupdate itself. The difficulty is that the BIND dynamic DNS configuration is a pain. You have to generate a key, update configurations, and modify zone files. The README file in the distribution leads you through the process, so I hope that's some help to even DNS newbies.

Stay tuned ... in my next blog entry I'll provide some further information on deploying web-nsupdate.