Dynamic DNS (DDNS)? -How it Works and Why Use It?

dynamic-dnsDynamic DNS keeps DNS records automatically up to date when an IP address changes.

Dynamic DNS is used in large networks that host internal services, and use their own internal DNS and DHCP servers.

However small companies, and home networks don’t normally have their own DNS server so why would they need Dynamic DNS ?

In this tutorial we look at how dynamic DNS works and how to set it up on a home router. (quick links)

 Dynamic DNS (DDNS) -Setup and Use

Dynamic DNS Services are used by small companies and individuals when they want to publish a service on the Internet, and that service is hosted within an internal or home network.

Home networks typically uses a NAT router to connect to the internet which means that devices located on the internal network aren’t accessible from the Internet.

In the following discussion we are going to assume that we want to make a web server located on an internal server available on the internet.

The network diagram below shows the configuration

The Internal IP address is assigned to the internal server by the NAT router and via the  DHCP service.

However when making a service available on the Internet we will usually give it a static internal IP address.

To make the web service available on the internet we use a technique called port forwarding ( see the  port forwarding  and Internal vs external IP address tutorials for more details).

Now our web server appears to our external client to be located at IPex and on port Portex.

If we put some typical numbers into this we will see our web server at

Ip Address= and on Port 80

All we need now do is to tell our external client to use these values.

However the external IP address IPex ( may also be dynamically assigned by the ISP, and we cannot make it static unless we pay for a static address.

In addition, the external client has to remember the IP address.

Dynamic DNS Service

If we now introduce a Dynamic DNS service into the picture.

With Dynamic DNS  we assign the web server a name which we can then give to external clients. This name is fixed and provided by the DDNS service provider.

We then assign the external IP address to the name.

Now because this external IP address will change periodically we will need to update the DNS record periodically.

We could of course do this manually, but that would be very unreliable as you don’t know when it has changed unless you check.

Instead the ability to automatically update the DNS server records is built into most NAT routers.

Here is a screen shot of the Dynamic DNS configuration page of my NAT router (BT Home Hub).


The configuration involves entering the name of your DDNS service provider DNS server and your login details.

When you apply it you should get a connected confirmation.


If you get username/password incorrect check you login details and retry.

Registering with a DDNS Service Provider

Before you can enable Dynamic DNS you will need an account from a DDNS provider.

There are several providers available. Most provide a free service with a premium upgrade.

The main providers all work in a similar way and the registration process is simple. For this tutorial I will use NO-IP.

You will need to create a host name for the IP address, and select from one of the available domain names provided by the provider, and enter a host name.

Below is the name form for No-IP



Dynamic DNS (DDNS) Not Supported on Router!

If your router doesn’t support DDNS updates you can get a special DDNS update client that you install on a machine on your local network that does the same job.

The only problem with this approach is that the machine needs to be constantly running.

Testing Your DDNS Configuration

Go to the ping command and test that you can access the IP address by pinging the domain name which consists of the host name +domain name.


Dynamic DNS (DDNS) Video

Here is a video that covers the above:

DDNS Common Uses

Although it is used by gamers and tech Geeks it is probably going to see more widespread adoption in remote security/surveillance and control areas.

Without Dynamic DNS how would you access your cameras from the Internet?

Common Questions and Answers

Q-What is the difference between dynamic DNS (DDNS) and DNS?

A- Dynamic DNS is a feature of DNS. Early DNS systems were static and the IP addresses and name mapping were entered manually. Dynamic DNS updates the Name- IP mappings automatically when the IP address changes.

Q- How do I find my external IP address?

A- Go to Google an type what’s my IP address.



Q- Should I enable DDNS on my router?

A- Normally no. You only need it when providing services to Internet based clients.

Q- Is Dynamic DDNS the same as port forwarding?

A- No- port forwarding makes a service available on an Internet address (external address). DDNS assigns a name to this external address and updates if the address changes.

Q- Does Dynamic DNS use the same port as DNS?

A- Yes UDP/TCP port 53

Q – Do I need a special DDNS client to use DDNS?

A– No it uses the standard DNS client found in all modern clients

Q- Should I enable or disable DDNS on my router?

A- DDNS is normally disable by default and you only need to enable it if you need to use it and you have a DDNS provider account.


Dynamic DNS (DDNS) is very useful if you need to access internal network services from across the Internet.

It isn’t designed for hosting a business website, for that you will need standard web hosting.

Related Articles and Resources:


Please Let me Know if you found it Useful
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  1. Hi Steve. I have a webserver running on my Pi device. I have router which giving internet access to my PI. However the external public address I get from router detail is different from the one I find in google(whatsmyip). I think this caused by NAT router configuration of my ISP. Which one of this public IP address should I use for me to access my PI from outside world and for my port forwarding to work correctly. Pls advise

  2. Hi Steve,

    I am trying to solve a problem with DDNS not updating on laptops as we move to different locations within our business. Any thoughts on where to start poking around to resolve this?

  3. Dear Steve, You have produced an excellent document that removes some the mystique associated with DDNS and has allowed me to be able now to view my security cameras from anywhere. What I still need to do is receive email notification of motion detection. I would appreciate any help.
    Regards, Sidney Robson

    1. Glad you found it useful. I would need some more information in order to try an help with that. If you could point me to the manual. Are you using a home automation system currently?

  4. How do you stop a ddns from being created basically stop someone from hacking onto my security cameras and deleting incriminating video.

    1. On a home network you don’t normally have DDNS but mDNS. However neither would stop hacking you need to improve the security on your cameras.
      I don’t use security cameras and am not s security expert so I can’t advise you on that.

  5. Is their such thing as : ‘ISP Is blocking ports or inbound connections’. I tried using this trick 10 to 15 days back and no matter what whether I am changing my IP address or my port address (on Local machine); when I am trying to access my website then the changes can be seen in the ip address and the port number online, but even then I am unable to access my website as it says something like : ‘Connection timed out’.

    Because of this I gave up and purchased hosting on namecheap.

    1. Sorry for the late reply but I was not notified of the comment.
      They could block it but it is doubtful. However you are better having hosting on the Internet.

  6. I just registered DynDNS pro as trial.
    I have multiple devices under one router. How do I configure router or the DynDNS so can access all the devices? I have assigned different ports for each device. When I try to access, every time, it goes to only one same device. Is there are way to access all devices under one router with dynamic IP?

    1. Each device needs a unique name
      device1.ddns.net –> device1
      device2.ddns.net –> device2

  7. I got a low-end external VPS, for webpage, how can I use it to

    1) set up UDP hole punching on my home network, so I don’t need to open a port in my router,

    2) have my own version of noip for home network, I don’t like using noip, because I constantly need to log into their site, and extend it every few weeks.

    1. Hi
      Never tried hole punching but you would need server software to do it.
      As for noip DNS then this is not possible as you need to be part of the global dns network which is restricted.
      Sorry can’t be more helpful

  8. why do we need an account somewhere to get this done? why isn’t there an app that can update dns records without having to use an external service?

  9. I would like to know do I need to add new hostnames to my router for each new html host? I’m presuming the router is not narrow and allocates many IP numbers to its clients, and if it was only one client my PC then is a dynamic IP name needed?

    1. For one host then manual assignment is ok.however using the router to do it is more flexible as I’m sure you have other devices like phones.
      Regarding several other questions I think you are a bit confused with hoes names and IP addresses . Suggest you start here

      Apache as far as I am aware cannot assign host names.
      The router will support as many html hosts as you put on the server. The server will probably be the problem not the router.All that needs to be done on the router is to configure port forwarding.

  10. If I tapered my router to assign my PC the IP number and use Apache to assign a host name and run a virtual host and add it into my router do you recommend a dynamic name being added to the router, does it affect devices connecting to my PC ?

  11. I second IROA, this is a great article!

    Correct me if I am wrong, but do not most home automation devices create a “hidden” DDNS server during their installation?

    Is there someway I can find all of these on my home LAN?

    1. No they don’t as far as I know. They may support MDNS (multicast DNS) so that they can locate devices on the local network.

  12. This is the best article about DNS and DDNS Ive ever seen over the internet. ISP changed my static ip onto dynamic. You are a legend, this is amazing!!!

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