Using Google Public DNS

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• Configuringyour network settings to use Google Public DNS
• Testingyour new settings
• Diagnosingresolution problems
• Switchingback to your old DNS settings

Configuring your network settings to useGoogle Public DNS

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 nameservers are automatically set by your ISP via the Dynamic HostConfigurationProtocol (DHCP). To use Google Public DNS, you need to explicitlychange the DNS settings in your operating system or device to use theGooglePublic DNS IP addresses. The procedure for changing your DNS settingsvaries according to operatingsystem and version (Windows, Mac or Linux) or the device (computer,phone, or router). We give general procedures here that might not applyfor yourOS or device; please consult your vendor documentation forauthoritativeinformation.

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 apiece of paper. It is very important that you keep these numbers forbackup purposes, in case you need to revert to them at any time.
After changing your settings, if you encounter a problem andcannot connect to the Internet, please call our supportnumbers for troubleshooting instructions.
We also recommend that you download this pageand print it, in the event that you encounter a problem and need torefer to these instructions.

Google Public DNS IP addresses

The Google Public DNS IP addresses are as follows:

• 8.8.8.8
• 8.8.4.4

You can use either number as your primary or secondary DNSserver. You can specify both numbers, but do not specify one number asboth primary and secondary.

Changing your DNS servers settings

Because the instructions differ between differentversions/releases of each operating system, we only give one version asan example. If you need specific instructions for your operatingsystem/version, please consult your vendor’s documentation. You mayalso find answers on our usergroup.
Many systems allow you to specify multiple DNS servers, to becontacted in apriority order. In the following instructions, we provide steps tospecify onlythe Google Public DNS servers as the primary and secondary servers, toensure that your setupwill correctly use Google Public DNS in all cases.

Microsoft Windows

DNS settings are specified in the TCP/IPProperties window for the selected networkconnection.
Example: Changing DNS server settings on MicrosoftWindows 7

1. Go the Control Panel.
2. Click Network and Internet, then Networkand Sharing Center, and click Change adapter settings.
3. Select the connection for which you want to configureGoogle Public DNS. For example:
   • To change the settings for an Ethernet connection,right-click Local Area Connection, andclick Properties.
   • To change the settings for a wireless connection,right-click Wireless Network Connection, and click Properties.

   If you are prompted for an administrator password or confirmation, typethe password or provideconfirmation.

4. Select the Networking tab. Under Thisconnection uses the following items, click InternetProtocol Version 4 (TCP/IPv4), and then click Properties.
5. Click Advanced and select the DNStab. If there are any DNS server IP addresses listed there, write themdown for future reference, and remove them from this window.
6. Click OK.
7. Select Use the following DNS server addresses.If there are any IPaddresses listed in the Preferred DNS server or AlternateDNS server, write them down for future reference.
8. Replace those addresses with the IP addresses of the GoogleDNSservers: 8.8.8.8 and 8.8.4.4.
9. Restart the connection you selected in step 3.
10. Test that your setup is working correctly; see Testing your new settingsbelow.
11. Repeat the procedure for additional network connections youwant to change.

Mac OS X

DNS settings are specified in the Networkwindow.
Example: Changing DNS server settings on Mac OS 10.5

1. From the Apple menu, click SystemPreferences, then click Network. 
2. Ifthe 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 configureGoogle Public DNS. For example:
   • To change the settings for an Ethernet connection,select Built-In Ethernet, andclick Advanced.
   • To change the settings for a wireless connection,select Airport, and click Advanced.
4. Select the DNS tab.
5. Click + to replace any listed addresses with, or add, theGoogle IPaddresses at the top of the list: 8.8.8.8and 8.8.4.4.
6. Click Apply and OK.
7. Test that your setup is working correctly; see Testing your new settingsbelow.
8. Repeat the procedure for additional network connections youwant to change.

Linux

In most modern Linux distributions, DNS settings areconfigured through Network Manager.
Example: Changing DNS server settings on Ubuntu

1. In the System menu, click Preferences,then click Network Connections.
2. Select the connection for which you want to configureGoogle Public DNS. For example:
• To change the settings for an Ethernet connection, selectthe Wired tab, then select your network interfacein the list. It is usually called eth0.
• To change the settings for a wireless connection, selectthe Wireless tab, then select the appropriatewireless network.
3. Click Edit, and in the window thatappears, select the IPv4 Settings tab.
4. If the selected method is Automatic (DHCP),open the dropdown and select Automatic (DHCP) addresses onlyinstead. If the method is set to something else, do not change it.
5. In the DNS servers field, enter theGoogle Public DNS IP addresses, separated by a space:8.8.8.8  8.8.4.4
6. Click Apply to save the change. If youare prompted for a password or confirmation, type the password orprovide confirmation.
7. Test that your setup is working correctly; see Testing your new settingsbelow.
8. Repeat the procedure for additional network connections youwant to change.

If your distribution doesn’t use Network Manager, your DNSsettings are specified in /etc/resolv.conf.
Example: Changing DNS server settings on a Debianserver

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 lineswith, or add, the following lines:

   nameserver 8.8.8.8nameserver 8.8.4.4

4. Save and exit.
5. Restart any Internet clients you are using.
6. Test that your setup is working correctly; see Testing your new settingsbelow.

Additionally, if you are using DHCP client software thatoverwritesthe settings in /etc/resolv.conf, you will need to set up the clientaccordingly by editing the client’s configuration file.
Example: Configuring DHCP client sofware on a Debianserver

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 followingline:

   prepend domain-name-servers 8.8.8.8, 8.8.4.4;

5. Save and exit.
6. Restart any Internet clients you are using.
7. Test that your setup is working correctly; see Testing your new settingsbelow.

Routers

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

To change your settings on a router:

1. In your browser, enter the IP address to access therouter’s administration console. 
2. When prompted, enter the password to access networksettings.
3. Find the screen in which DNS server settings arespecified. 
4. If there are IP addresses specified in the fields for theprimary and seconday DNS servers, write them down for future reference.
5. Replace those addresses with Google IPaddresses: 8.8.8.8 and 8.8.4.4.
6. Save and exit.
7. Restart your browser.
8. Test that your setup is working correctly; see Testing your new settingsbelow.

Mobile or other devices

DNS servers are typically specified under advanced wi-fisettings. However, as every mobile device uses a different userinterface for configuring DNS server settings, we provide only ageneric procedure below. For moreinformation, please consult your mobileprovider’s documentation.
To change your settings on a mobile device:

1. Go to the screen in which wi-fi settings arespecified.
2. Find the screen in which DNS server settings arespecified.
3. If there are IP addresses specified in the fields for theprimary and seconday DNS servers, write them down for future reference.
4. Replace those addresses with Google IPaddresses: 8.8.8.8 and 8.8.4.4.
5. Save and exit.
6. Test that your setup is working correctly; see Testing your new settingsbelow.

Testing your new settings

To test that the Google DNS resolver is working:

1. From your browser, type in a hostname, such ashttp://www.google.com. If it resolves correctly,bookmark the page, and try accessing the page from the bookmark. Ifboth 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 canuse http://18.62.0.96/(which points to the website http://www.eecs.mit.edu/) asthe URL*. If this works correctly, bookmark the page, and try accessingthe page from the bookmark. If these tests work(but step 1 fails),then there is a problem with your DNS configuration; check the stepsabove to make sure you haveconfigured everything correctly. If these tests do not work,go tostep 3.
3. Roll back the DNS changes you made and run thetests again. If the tests still do not work, then there is a problemwith your network settings; contact your ISP or network administratorfor assistance.

* Google thanks MIT for granting permission to usethis URL for the purposes of testing web connectivity.

Diagnosing resolution problems

If you are encountering problems when resolving particularnames,and want to verify whether the problem is with Google Public DNS,please try running the following diagnostic procedures. If you want toreport a problem to the GooglePublic DNS usergroup, please copy and paste the results of the commands inyour email.This information is vital to help us to identify the cause of theproblem.

Step 1: Verify that your client can communicate with theGoogle Public DNS servers

Open a command prompt, and run the following command:
On Windows:

tracert -d 8.8.8.8

On Mac OS X:

/usr/sbin/traceroute -n -w 2 -q 2 -m 30 8.8.8.8

On Linux:

sudo traceroute -n -w 2 -q 2 -m 30 8.8.8.8

If the last line of the output does not list 8.8.8.8 as thefinal hop, or if there are significant timeouts, there may be a networkproblem preventing youfrom contacting our servers. Please include the output of the commandin any communication with the Google Public DNS team.
If the last line of the output does list 8.8.8.8 as the finalhop, continue to step 2.

Step 2: Verify that Google Public DNS can resolve theselected hostname

At the command prompt, run the following command, wherehostname is thename that you were having difficulty resolving:
On Windows:

nslookup -debug hostname 8.8.8.8

On Mac and Linux:

dig @8.8.8.8 hostname

If the the output shows an answer section with an A record forthehostname, then Google Public DNS is able to resolve the name. Checkyour settings to make sure your system is correctly configured to useGoogle Public DNS. If you are still unable to solve the problem, pleaseinclude the output of the command in any communication with the GooglePublic DNS team.
If the output does not show an answer for the hostname,continue to step 3.

Step 3: Verify that another open resolver can resolve theselected hostname

At the command prompt, run any one of the following commands,where hostname is the name that you were havingdifficultyresolving:

nslookup hostname 4.2.2.1

nslookup hostname 4.2.2.2

nslookup hostname 208.67.222.222

nslookup hostname 208.67.220.220

(The first two commands test Level 3′s DNS servers. The lasttwo commands test OpenDNS’ DNS servers.)
If you are not able to get a successful result, this meansthat there is most likely a problem with the server you are trying tocontact. Wait some time and try running the tests again. This may be atemporary problemon the server’s side that will likely resolve itself eventually. If itdoes not, you should contact the owner of the server.
If you do get a successful result, there may be a problem withGoogle Public DNS. Please include the outputof this command and the one from step 2 in any communicationwith the Google Public DNS team.

Switching back to your old DNS settings

If you had not previously configured any customized DNSservers, toswitch back to your old settings, in the window in which you specifiedthe Google IP addresses, select the option to enable obtaining DNSserver addresses automatically, and/or delete the Google IP addresses.This will revert your settings to using your ISP’s defaultservers.
If you need to manually specify any addresses, use theprocedures above to specify the old IP addresses.
If necessary, restart your system.