What is a DNS server?

We explain what a DNS server is, how it works and how to avoid DNS hijacking

Networks servers

Domain Name Servers, also known by the acronym DNS, are widely considered to be the backbone of the world wide web. However, in more specific terms, it can be compared to more of rolodex holding the details for every website and domain accessible to the internet or private network. Thanks to the DNS, devices such as laptops, desktops, or tablets can be connected to whichever website a user wants to visit.

You might have also come across NS, or nameservers, especially when switching hosts while running a website. These are under the umbrella of DNS and hold a significant role in hosting. Nameservers focus on handling queries regarding the location of the services offered by DNS, making it possible to use domains instead of IP addresses.

When is a DNS server used?

As you open your web browser of choice and type in the URL of a website you want to visit, a DNS resolver will perform a scan of the web in order to identify the IP address of that domain name. By examining one DNS server at a time, the resolver will make an effort to identify the location of the stored information.

As soon as the resolver manages to pinpoint the location of the IP address, it allows for content elements to be filtered through to the user who will then be able to look at the website as it is intended to be viewed. These content elements may include various examples of user interface (UI), from images and pages to other visual objects.

How is the DNS server set up?

Internet Service Providers (ISPs) normally run their own DNS with a router serving as the gateway between a device and the DNS. IP queries are sent to the ISP’s DNS that look for where website assets are kept.

Are some DNS servers faster than others?

The pace at which queries can be resolved is heavily dependent on the location of a DNS server, and being further away from a server may mean that connections and responses will be slower. That is why the majority of ISPs make sure to have their DNS servers distributed across the globe, so that their customers can find themselves near one whenever they need to power up their websites.

Another aspect worth considering is the distance between organisations’ sites and their visitors. Although not always apparent, those who live closer to where the site is located experience a service faster than those based on the other side of the world.

One way to speed up the DNS lookup is to have already visited a page before. This is because the IP address and hostname will have already gone through the resolution process, meaning that the information will be stored on the users’ devices. Hence they will not be forced to search for the connection from scratch when they enter the name of the website into the address bar.

Another way to resolve speed issues is by using a content delivery network (CDN). These aim to deliver content faster when resolving queries, although it’s not considered a solution directly affecting the DNS. CDNs work by placing content into a location within a local proximity to the user visiting the website. Even if the DNS takes a while longer to resolve, the entirety of the content, such as the pictures and assets which comprise its UI, will be delivered to machines faster due to the considerably shorter length that they have to travel.

DNS server security concerns

A man maintaining servers

Sometimes, DNS servers can be hijacked by hackers, leading unsuspecting victims to fake websites that appear to be the site you're trying to reach, but the IP address has been changed to appear as though it's the genuine site.

To avoid falling victim to such scams, you should ensure your antivirus and malware detection tools are up to date and if you see an invalid certificate warning message, it's a good idea not to head to the website, especially if it's asking for sensitive information.

What happens when a DNS server fails to respond?

When you connect one of your devices to a network, you may find that it fails to establish an internet connection, and you’re met with a ‘DNS server not responding error message. There are a few reasons why this might happen, and a handful of ways to go about fixing the problem.

These problems are normally caused by problems on the user’s end, as opposed to problems server-side, and could be a result of issues with the network connection, misconfigure DNS settings, or a browser in need of updating. Temporary server outages also generate the error message. In theory, you could fix the problem by switching to another browser, if the one you’re using needs to be updated, or you can take a few other measures including disabling connections, changing your DNS server, or flushing the DNS cache.

Occasionally, you may be met with a message reading: “your computer appears to be correctly configured, but the device or resource (DNS server) is not responding”. To resolve this problem, you can try a number of things. Firstly, make sure that the proxy server is disabled in your browser settings, and that your PC’s power-saving settings are disabled. You can also try to tweak your network settings so your device chooses the DNS server address automatically. 

To do this on Windows 10, you’ll need to navigate to the Network and Sharing Centre and click on the name of your Wi-Fi connection. Select ‘Properties’ before finding ‘Internet Protocol Version 4’ on the list, and choosing ‘Properties’ again. Select the options ‘Obtain an IP address automatically’ and ‘Obtain DNS server address automatically. Then return to the list and find ‘Internet Protocol Version 6’, open properties, and do the same.

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