Using DYNU as Custom Dynamic DNS on DD-WRT Router

This is a guide to setup a custom dynamic DNS on dd-wrt, specifically I have my dd-wrt router connected to my externally facing modem - it doesn't have a direct WAN connection (this is important). The configuration details should however work in most cases, it will be a simple process of changing "Do not use external ip check"

I am personally using the Netgeart 3500L, which I paid $180 for a few years ago, but you can get at a steal now - NETGEAR WNR3500L RangeMax Wireless-N300 Gigabit Router with USB - Manufacturer Refurbished

I decided to create this guide due to recent issues with no-ip.org.  Other than the fact that they were served with a take-down notice from Microsoft, I was getting tired of logging in every 30 days.  I came across the following site:

http://www.gnutomorrow.com/best-free-dynamic-dns-services-in-2013/

And decided to go with dynu.com.  The configuration is as follows, and I got most of the information from the following page with their api:

http://www.dynu.com/default.aspx?page=dnsapi

You should replace the following fields in the screenshot:

youusername with your the username found under Main Menu >> Dynamic DNS Service Details >> General Settings in your dynu.com account settings - I do not believe that your email will work.
yourpassword with yourpassword to log in to your account
yourserver with your configured dynu hostname

Note that the "Do not use external ip check" is set to no, so that the router determines it's external IP and sends it - since it isn't connected directly, and therefore has no WAN address.