Knowledgebase: Domains > DNS
Using Public DNS on Linux
Posted by Aaron Eaton on 15 October 2015 03:24 PM

When you use Google Public DNS, you are changing your DNS "switchboard" operator from your ISP to Google Public DNS.

In most cases, the IP addresses used by your ISP's domain name servers are automatically set by your ISP via the Dynamic Host Configuration Protocol (DHCP). To use Google Public DNS, you need to explicitly change the DNS settings in your operating system or device to use the Google Public DNS IP addresses. The procedure for changing your DNS settings varies according to operating system and version (Windows, Mac or Linux) or the device (computer, phone, or router). We give general procedures here that might not apply for your OS or device; please consult your vendor documentation for authoritative information.

Important: Before you start

Before you change your DNS settings to use Google Public DNS, be sure to write down the current server addresses or settings on a piece of paper. It is very important that you keep these numbers for backup purposes, in case you need to revert to them at any time.

We also recommend that you print this page, in the event that you encounter a problem and need to refer to these instructions.

Google Public DNS IP addresses

The Google Public DNS IP addresses (IPv4) are as follows:

  • 8.8.8.8
  • 8.8.4.4

The Google Public DNS IPv6 addresses are as follows:

  • 2001:4860:4860::8888
  • 2001:4860:4860::8844

You can use either address as your primary or secondary DNS server. You can specify both addresses, but do not specify one address as both primary and secondary.

You can configure Google Public DNS addresses for either IPv4 or IPv6 connections, or both.

Change your DNS servers settings

Because the instructions differ between different versions/releases of each operating system, we only give one version as an example. If you need specific instructions for your operating system/version, please consult your vendor's documentation.

Many systems allow you to specify multiple DNS servers, to be contacted in a priority order. In the following instructions, we provide steps to specify only the Google Public DNS servers as the primary and secondary servers, to ensure that your setup will correctly use Google Public DNS in all cases.

Linux

In most modern Linux distributions, DNS settings are configured through Network Manager.

Example: Changing DNS server settings on Ubuntu

  1. Click System > Preferences > Network Connections.
  2. Select the connection for which you want to configure Google Public DNS. For example:
    • To change the settings for an Ethernet connection, select the Wired tab, then select your network interface in the list. It is usually called eth0.
    • To change the settings for a wireless connection, select the Wireless tab, then select the appropriate wireless network.
  3. Click Edit, and in the window that appears, select the IPv4 Settings or IPv6 Settings tab.
  4. If the selected method is Automatic (DHCP), open the dropdown and select Automatic (DHCP) addresses only instead. If the method is set to something else, do not change it.
  5. In the DNS servers field, enter the Google Public DNS IP addresses, separated by a space:
    • For IPv4: 8.8.8.8 and/or 8.8.4.4.
    • For IPv6: 2001:4860:4860::8888 and/or 2001:4860:4860::8844.
  6. Click Apply to save the change. If you are prompted for a password or confirmation, type the password or provide confirmation.
  7. Test that your setup is working correctly
  8. Repeat the procedure for additional network connections you want to change.

If your distribution doesn't use Network Manager, your DNS settings are specified in /etc/resolv.conf.

Example: Changing DNS server settings on a Debian server

  1. Edit /etc/resolv.conf:

     
    sudo vi /etc/resolv.conf
  2. If any nameserver lines appear, write down the IP addresses for future reference.

  3. Replace the nameserver lines with, or add, the following lines:

    For IPv4:

     
    nameserver 8.8.8.8
    nameserver
    8.8.4.4

    For IPv6:

     
    nameserver 2001:4860:4860::8888
    nameserver
    2001:4860:4860::8844
  4. Save and exit.

  5. Restart any Internet clients you are using.
  6. Test that your setup is working correctly

Additionally, if you are using DHCP client software that overwrites the settings in /etc/resolv.conf, you will need to set up the client accordingly by editing the client's configuration file.

Example: Configuring DHCP client sofware on a Debian server

  1. Back up /etc/resolv.conf:

     
    sudo cp /etc/resolv.conf /etc/resolv.conf.auto
  2. Edit /etc/dhcp3/dhclient.conf:

     
    sudo vi /etc/dhcp3/dhclient.conf
  3. If there is a line containing domain-name-servers, write down the IP addresses for future reference.

  4. Replace that line with, or add, the following line:

    For IPv4:

     
    prepend domain-name-servers 8.8.8.8, 8.8.4.4;

    For IPv6:

     
    prepend domain-name-servers 2001:4860:4860::8888, 2001:4860:4860::8844;
  5. Save and exit.

  6. Restart any Internet clients you are using.
  7. Test that your setup is working correctly

Routers

Every router uses a different user interface for configuring DNS server settings; we provide only a generic procedure below. For more information, please consult your router documentation.

To change your settings on a router:

  1. In your browser, enter the IP address to access the router's administration console.
  2. When prompted, enter the password to access network settings.
  3. Find the screen in which DNS server settings are specified.
  4. If there are IP addresses specified in the fields for the primary and seconday DNS servers, write them down for future reference.
  5. Replace those addresses with the Google IP addresses:
    • For IPv4: 8.8.8.8 and/or 8.8.4.4.
    • For IPv6: 2001:4860:4860::8888 and/or 2001:4860:4860::8844.
  6. Save and exit.
  7. Restart your browser.
  8. Test that your setup is working correctly

Test your new settings

To test that the Google DNS resolver is working:

  1. From your browser, type in a hostname (such as http://www.google.com/). If it resolves correctly, bookmark the page, and try accessing the page from the bookmark. If both of these tests work, everything is working correctly. If not, go to step 2.
  2. From your browser, type in a fixed IP address. You can use http://18.62.0.96/ (which points to the website http://www.eecs.mit.edu/) as the URL.1 If this works correctly, bookmark the page, and try accessing the page from the bookmark. If these tests work (but step 1 fails), then there is a problem with your DNS configuration; check the steps above to make sure you have configured everything correctly. If these tests do not work, go to step 3.
  3. Roll back the DNS changes you made and run the tests again. If the tests still do not work, then there is a problem with your network settings; contact your ISP or network administrator for assistance.

Switch back to your old DNS settings

If you had not previously configured any customized DNS servers, to switch back to your old settings, in the window in which you specified the Google IP addresses, select the option to enable obtaining DNS server addresses automatically, and/or delete the Google IP addresses. This will revert your settings to using your ISP's default servers.

If you need to manually specify any addresses, use the procedures above to specify the old IP addresses.

If necessary, restart your system.

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