Using local DNS caching

I’ve found a very easy way to use local DNS caching on the Mac: simply setup Internet sharing from one device you don’t use, to another you don’t use. Since I almost always get my Internet access through wireless, I’ve setup my system to share my Fireware port to anyone connected to my Ethernet port.

Although this sharing setup doesn’t do any sharing, what it does do is to cause OS/X to run a local DHCP server and a local DNS server. This local DNS server takes its nameserver addresses from your current Internet configuration (in my case, wireless), so everything is automatically setup to cache DNS from the nameservers you’re actually using.

The only thing necessary to do is to change /etc/resolv.conf to point at your new local nameserver. Using the Network Preferences Pane, find out what your local Ethernet address is (to use my example; you’ll have to find the IP of the interface you’re sharing from). Now edit /etc/resolv.conf so it looks something like this:


In my case, my local Ethernet interface gets set to when I’m using sharing. You may need to setup a cron job (check out the utility CronniX) in order for your resolv.conf to get overwritten each time with this setting.

Now site back and enjoy the added speed of cached DNS! This is especially helpful on connections that drop packets a lot, since I find a great number of the “pauses” in my Internet usage all relate to lagged out DNS lookups.