What is Dynamic DNS and how does it work?


Domain Name Systems (DNS) are one of the backbone technologies of the Internet. It allows us to find and navigate websites.

DNS exists in two flavors: dynamic and static. And although they are both different, they perform the same basic function. Today we are going to focus mainly on what Dynamic DNS (DDNS) is and how it works.

What is Dynamic DNS?

To understand DDNS, you first need to understand a bit more about what static DNS is.

A static DNS is a way to maintain records of devices and information on the Internet. DNS acts like a phone book because it stores the domain names of resources, such as websites, against their IP addresses.

In a DNS record, each domain name has a corresponding IP address. For example, if you enter the domain name of a website into a DNS lookup tool such as thisyou will get the IP address that corresponds to that particular domain name.

Now here’s the problem: if the IP address corresponding to a certain domain name changes and the change is not reflected in the DNS records, no one on the Internet will be able to connect to the affected website.

Only once the IP address is corrected in the DNS records will users be able to access the website.

Dynamic DNS or DDNS aims to prevent this by updating domain name records with the dynamically changing IP address. DDNS is especially important for users who host resources on their home Internet connection.

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Internet Service Providers (ISPs) have a fixed pool of IP addresses to assign. Thus, they cannot assign static IP addresses to individual users, as they would run out of addresses.

To solve this problem, ISPs assign IP addresses dynamically. Addresses change as and when necessary. As you can probably see, this dynamic change of IP addresses will cause the problem described above.

How does a DDNS work?

You will recall earlier in this article that a DNS is a decentralized registry of domain names mapped to IP addresses. These IP addresses are fixed. They are not supposed to change.

If changed, the domain names corresponding to these IP addresses will not work until the IP addresses are corrected in the registry.

IP correction in the registry can be done manually or automatically. In the case of a static DNS, updating the registry requires manual work.

DDNS, on the other hand, automatically updates the registry whenever an IP address changes. DDNS services are often built into routers. They also run on host computers.

DDNS works by using custom hostnames mapped to individual devices/resources inside a network. For example, suppose you want to access a security camera placed on your front door from anywhere in the world. To do this, you will need an IP address that will allow you to navigate to the camera over the Internet.

However, if your ISP changes the IP address, the old IP address you were using to access the camera will not work.


Using a DDNS service to map a fixed, custom hostname to a resource ensures that you will always have access to the resource, even if the underlying IP address changes.

You can use your DNS to block and unblock websites

Since DNS is a record of domain names against their IP addresses, ISPs use this record as a way to filter websites. In other words, many ISPs use it to geo-block websites.

Now, if you can use a remote DNS server to hide your DNS address, you can effectively bypass geo-restrictions without using a VPN.


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