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Choosing the correct DNS Servers

Contents

Parts of this page are copied from Google Public DNS Documentation which is licensed under the Creative Commons Attribution 4.0 License.

Configure your network settings to use CS Department DNS Servers

If you are using your own personal computer on the CS Department network, the Dynamic Host Configuration Protocol (DHCP) automatically configures your system to use the department’s DNS servers. If you have a static IP address, you will need to set your DNS servers manually. The procedure for changing your DNS settings varies according to operating system and version (Windows, Mac, Linux, or Chrome OS) or the device (computer, phone, or router). We give general procedures here that might not apply for your OS or device; consult your vendor documentation for authoritative information.

Depending on your system you may also have the option of enabling a new privacy-oriented feature called DNS-over-TLS. This feature provides privacy and security for the DNS messages sent between your device and the DNS servers. The CS department does not currently support DNS-over-TLS.

DNS Server IP Addresses

The Computer Science Department and the University Division of Information Technology operate a number of different DNS servers. How you are connected to the network will change which servers you should choose. You can find our recommended servers (and see other information about your network connection) on our IP Address page. A machine readable version is also available:

Because this information can change depending on which part of the network you are connected to, you should try to view the ip page on the system you are changing settings on.

For example, if you want to find the correct IP address for your Linux server, you can use the command
curl https://helpdesk.cs.umd.edu/faq/connecting/ip.txt.

If your DNS isn’t working at all, you can replace helpdesk.cs.umd.edu with the IP address of the FAQ pages (and ignore the SSL certificate):
curl -k https://128.8.127.13/faq/connecting/ip.txt.

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 let you to specify multiple DNS servers, to be contacted in priority order. Depending on which network segment you are on, we may recommend two or more DNS servers. Some computers will let you select only two or you may be able to add all of them. The IP Address page will have more information about the choice of servers.

Note: Depending on your network setup, you may need administrator/root privileges to change these settings.

Windows

DNS settings are specified in the TCP/IP Properties window for the selected network connection.

Example: Changing DNS server settings on Windows 10

  1. Go to the Control Panel.

  2. Click Network and Internet > Network and Sharing Center > Change adapter settings.

  3. Select the connection for which you want to configure CSD/UMD DNS. For example:

    • To change the settings for an Ethernet connection, right-click the Ethernet interface and select Properties.
    • To change the settings for a wireless connection, right-click the Wi-Fi interface and select Properties.

    If you are prompted for an administrator password or confirmation, type the password or provide confirmation.

  4. Select the Networking tab. Under This connection uses the following items, select Internet Protocol Version 4 (TCP/IPv4) and then click Properties.

  5. Click Advanced and select the DNS tab. If there are any DNS server IP addresses listed there, write them down for future reference, and remove them from this window.

  6. Click OK.

  7. Select Use the following DNS server addresses. If there are any IP addresses listed in the Preferred DNS server or Alternate DNS server, write them down for future reference.

  8. Replace those addresses with the IP addresses from the IP Address page.

  9. Test that your setup is working correctly; see Test your new settings.

  10. Repeat the procedure for additional network connections you want to change.

macOS

DNS settings are specified in the Network window.

Example: Changing DNS server settings on macOS 10.15

  1. Click Apple menu > System Preferences > Network.

  2. If the lock icon in the lower left-hand corner of the window is locked, click the icon to make changes, and when prompted to authenticate, enter your password.

  3. Select the connection for which you want to configure CSD/UMD DNS. For example:

    • To change the settings for a Wi-Fi connection, select Wi-Fi, and click Advanced.
    • To change the settings for an Ethernet connection, select Built-In Ethernet, and click Advanced.
  4. Select the DNS tab.

  5. Click + to replace any listed addresses with, or add, the servers listed on the IP Address page:

  6. Click OK > Apply.

  7. Test that your setup is working correctly; see Test your new settings.

  8. Repeat the procedure for additional network connections you want to change.

Testing

To test that the DNS resolver is working:

  1. From your browser, enter a hostname URL (such as http://www.google.com/). If it resolves correctly, quit the browser, load the page again and refresh it for several times to make sure the result is not from a cached web page.

    If all of these tests work, everything is working correctly. If not, go to the next step.

  2. From your browser, type in a fixed IP address. You can use https://128.8.127.4/ (which points to the department website) as the URL.

    If this works correctly, reload the page with a new opened browser to make sure the page is loaded from scratch. 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 the next step.

  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 the helpdesk.