DHCP Reservations Howto

I recently installed an Open Sprinkler PI system in my house. This is a great system from Ray’s Hobby which has its own web server. You can access it from a web browser or with an iPhone app which talks to the same server. But you need to access the web server using an ip address, and the easiest way to set the system up is using DHCP, which assigns its own ip addresses. The only way to know what address the OSPI was given is to look at your router’s DHCP table, which is a giant hassle.

That’s what DHCP reservations are for. Every router is different, but most have the ability to assign a consistent ip address in the DHCP range to a given device on the network. Here’s how it’s done using an Airport Extreme and Airport Utility:

  1. Open Airport Utility.
  2. Click on the picture of your router.
  3. Find the wireless client called ospi (you might have to scroll)
  4. Roll over that name and you’ll see a popup.
  5. Write down the hardware address in that popup.
  6. Click on edit and then the Network tab.
  7. Click on + in the DHCP Reservations section.
  8. Give it a nice description and Reserve Address By: Mac Address.
  9. Type in the hardware address you wrote down (including the colons)
  10. There will be an IPv4 address entered, you can keep that or change it. Either way, that will be your reserved ip address.
  11. Hit Save then Update, wait for the router to reboot and your all set!

Now you can enter that ip address in your mobile app and always be able to access your OSPI.

That all works fine as long as you’re connected to your wireless home network. But what if you want to control your sprinklers from anywhere in the world? Well, that’s the topic of another post.