How to configure a DNS server ?

Thanks to the Domain Name System (DNS), you do not have to memorize IP addresses like 216.58.215.46 to open an Internet site. You only need to remember the corresponding domain name, in this case google.com. DNS servers translate into simple terms the protocol for guiding computers on the Web.

They can also be changed to optimize the operation.

Why configure a DNS ?

In general, you default to your ISP's DNS servers. What is a DNS ? It is a service similar to a directory, linking web page names to their IP addresses. Thus, you will need configure a DNS server different, if your ISP has removed some domain names from the directory.

This technique therefore represents a alternative to VPN to bypass censorship.

In France, for example, sites like The Pirate Bay are absent from the DNS servers of the main market operators. These deletions are required by the State since the adoption of the HADOPI law. That said, a myriad of reasons can lead to the banning of DNS servers from SFR, Orange, Bouygues, Free… They can, for example, blocking domains or subdomains that are deemed dangerous.

Indeed, the meta-analysis of cyber attacks sometimes allow to to recurring locations (IP, name servers, DNS zones…). In this case, it is better to delete these DNS records to protect the system and the users. Such a decision will inevitably limit Internet access in the country.

On the other hand, ISP DNS servers are not not necessarily the fastest on the network. You may be penalized by the delays of your provider compared to other Internet players. Fortunately, technology companies offer the general public several alternative DNS servers.

You can use these services to reduce the response time on your DNS requests.

Where to find the DNS settings ?

If you want to configure a DNS server, you must first go to the settings dedicated button on the computer. The access path will however depend on your operating system. Under Windows for example, the DNS parameters are in the TCP/IP protocol properties of your network connection.

To find these parameters on Mac, open the Apple menu in the upper left corner of the desktop, near the Finder. Select System Preferences to access the settings panel. Then click on the Network icon. In the new window, you will see a list of all network connections.

The active connection is displayed in priority and preceded by a green dot.

Choose the connected network in the left panel, then press Advanced at the bottom right of the interface. The new page displayed will have several tabs leading to WINS, TCP/IP, Proxies, etc. Click on DNS.

You will discover the addresses of your DNS servers (priority and auxiliary).

If you use Ubuntu, click on the Network in the upper left part of the screen. The image may show two arrows or the Wi-Fi symbol, depending on your OS version. Press Edit connections to open the list of networks associated with the computer. Select the active connection.

Finally, left-click on the Edit button to view your current DNS settings.

What tools can be used to check the correct operation of a DNS server? ?

A DNS server works correctly when converting a domain name to an IP address. Response time may vary depending on your ISP and Internet connection. Nevertheless, the delay is relatively short in most cases.

The ping measurement allows you to observe the good functioning of your recursive server. You will need the CMD tool of Windows with this technique.

To access them, press the Start. Then look for cmd and click on the command prompt icon. Enter " ping [DNS server] "and then type Enter. However, you must enter the server address between the square brackets and not its current name. You will have to write, for example, 8.8.8.8 or 8.8.4.4, instead of Google Public DNS.

The server works, if the command succeeds.

You can also query the DNS server in the command prompt using " nslookup ". This command line is particularly interesting because of its cross-platform nature. It can indeed be executed on Windows, Mac and most Linux distributions. Writing the function returns "name server look up".

Specifically, you just need to enter the command: nslookup [your IP address]. This will give you the name and address of the DNS server. If the latter does not work, you will receive error messages or indications about the status of the request. The server responds correctly, if you find out its name, address and its role as primary, authoritative, master, slave

How to configure a DNS server on Windows ?

Go to the system settings for configure a DNS server on Windows. To do so, open the Start menu in the lower left corner of the screen. Click on the cogwheel icon to access the settings. You can also bring up the Settings interface with the key combination " Windows+I ".

In the displayed window, select the line Network and Internet. Then click on the Network and Sharing Center, and then click on Edit Map Settings. This link is located in the left pane under the Control Panel Home Page.

Right click on the active connection and select Properties at the bottom of the pop-up menu.

On the new interface, choose Internet Protocol version 4 (TCP/IPv4), then click on Properties near the Uninstall button. Check the option Use the following DNS server address to unlock the fields to be filled in. Keeping the example of Google, enter 8.8.8.8 in the Preferred DNS server box and 8.8.4.4 in Auxiliary DNS server.

Finally, press OK to validate the changes.

You must follow the same path for IPv6 queries. Select the Internet Protocol version 6 (TCP/IPv6) line and open the Properties. Scroll to the bottom of the window and unlock the fields to customize the DNS server.