Dynamic DNS for Your Pi

My last two posts talked about how I used a Raspberry Pi to act as a low-power home server that now mainly serves two functions: as a NAS box and as a Torrentbox. Now, there are a multitude of other things that we can do with the Raspberry Pi, and a lot of them are controllable using a web-based interface. This gives us ease of control using a lot of devices, but still limits us to the confines of our local network. This post will attempt to address that.

Why I Did It

I don’t have a static IP assigned to my home internet connection. This means that each time something forces my modem to disconnect and then reconnect, I will have a different public IP address. Not good if I want to set up remote access for, let’s say, my Deluge web interface, because I’d have to first figure out what my public IP address changes to, which means I’d have to go home and… well, you get the idea.

Hence, Dynamic DNS, or DDNS.

Port Forwarding

The first thing I need to do to make this work is to enable port forwarding. If you don’t know what it is, a simple Google search will get you all the info you need. For the sake of example, I’ll be forwarding port 22 to my Raspberry Pi’s port 22 so that I can access its ssh from outside my network.

Next, I need to set up the Dynamic DNS service. What it does is basically enable me to route all requests to a particular URL so that it reaches the IP address of my choice. There are two ways to go about doing this.

Free Dynamic DNS Service

A popular free Dynamic DNS service, DynDNS, apparently has stopped its free service. One of the free alternatives that many people start to use is NoIP. After signing up for free, I get to choose my subdomain.

Why a subdomain? Because it’s free.

After I have my subdomain setup, I can go ahead and download the DUC Client for Linux. There are plenty of instructions on the internet on how to set this up on a Raspbian Wheezy. After I got it up and running on boot on my Pi, I can sit back, relax, and have my Pi update its public IP address to the NoIP service. I can then access my Pi’s secure shell from anywhere by instructing PuTTY to connect to [mysubdomain].[my-no-ip-domain] at port 22.

There’s a catch, though. I’d have to reactivate the free subdomain every 30 days. Well, they gotta do something to get me to buy their paid services, right?

But wait… there’s another way.

Free Dynamic DNS Service With My Own Domain

One of the perks of having my own domain and hosting at IdWebHost is that I can have as many subdomains as I’d like, and it’s dirt cheap. Check their pricing tables for more info, and I also have to say kudos to their customer support team that runs 24/7.

Before I do anything else, I setup a subdomain and confirm that it is indeed accessible. I also check my A records using the Zone DNS Editor. This could be different for each hosting company, so I won’t go into its details here; it’s best to ask their customer support directly.

The Dynamic DNS service of my choice is CloudFlare. I’ve heard a lot about them, and most are positive reviews. Most important, though, is that they offer a free service package. I then enter add my domain and let CloudFlare scan my  DNS records.

After the usual sign-up – confirm email – activate 2-factor authentication routine, I proceeded with setting up my domain. I let CloudFlare scan my DNS records, and make sure that the new subdomain I added earlier is detected. If not, I just manually add a new A record, copying settings from my domain’s A record.

Next, I go and read an article about how to set up a custom script both on my hosted web and on my Pi to automatically check for public IP changes every 5 minutes. Just for fun, I changed the PHP script a bit so that it sends me an email every time it detects that my public IP address has changed.

Finally, I have to actually make the internet use CloudFlare’s DNS to make this all work. So I go to my IdWebHost management page, and set my nameservers to point to CloudFlare’s nameservers instead of IdWebHost’s. People usually say that DNS update propagation is slow as a slug and it takes up to 24 hours at a time to make the updates propagate. Not the case with CloudFlare. I just need to issue a “ipconfig /flushdns” on my Windows command prompt a few times to force an update.

A word of caution for this setup: because of the way some web hosting companies setup their CPanel sites as [domain]:[port], in other words it doesn’t use a subdomain for CPanel, you may need to tinker a little bit with your DNS settings so that CPanel doesn’t run through CloudFlare’s CDN. I chose to completely bypass CloudFlare’s CDN, except for this blog, because really the only thing I’m using from them is the Dynamic DNS service. Your mileage will vary.

Aftermath

Now, I have access to my home network that I can configure simply by configuring port forwarding on my router, and I don’t have to worry about my public IP address changing after a blackout (which unfortunately is a common thing on this side of the world).

As a matter of fact, my house just experienced a blackout today at about 9 a.m., at which time everybody was out working. At about 3.15 p.m., I was able to access my torrentbox from my cellphone. A query on my Pi’s uptime showed 12 minutes, which means that within 12 minutes of my Pi starting up, my new public IP was successfully propagated. Awesome!

2 Comments

  1. Eru

    One other alternative is using DD-WRT router and enable the DynamicDNS on the router. It will auto update to available DDNS provider every time ISP assign new IPs.

    I am using http://freedns.afraid.org . One simple but free service that is compatible with DD-WRT.

    Additional note for Indonesians. Some ISP close ports below 8000-ish. So on some rare cases need to open your preferred remote-web management on port above 8000-ish.

    • Yep, DD-WRT is also a great idea, but apparently my modem is not on their compatible devices list so that’s not an option for me.

      I also took a look at FreeDNS, but I think I read somewhere that if you register your domain there the community can then arbitrarily add and use subdomains to your domain? I don’t really know if that’s true because I don’t have an account there. How did it go for you?

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