- Configuring
your network settings to use Google Public DNS - Testing
your new settings - Diagnosing
resolution problems - Switching
back to your old DNS settings
Configuring your network settings to use
Google 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 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.
Note: We recommend that
only users who
are proficient with configuring operating system settings make
these changes.
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 number as your primary or secondary DNS
server. You can specify both numbers, but do not specify one number as
both primary and secondary.
You can configure Google Public DNS addresses for either IPv4 or IPv6 connections, or both.
Changing 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. You may
also find answers on our user
group.
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.
Note: Depending on your
network setup, you may
need administrator/root privileges to change these settings.
Microsoft Windows
DNS settings are specified in the TCP/IP
Properties window for the selected network
connection.
Example: Changing DNS server settings on Microsoft
Windows 7
- Go the Control Panel.
- Click Network and Internet, then Network
and Sharing Center, and click Change adapter settings. - Select the connection for which you want to configure
Google Public DNS. For example:- To change the settings for an Ethernet connection,
right-click Local Area Connection, and
click 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, type
the password or provide
confirmation. - To change the settings for an Ethernet connection,
- Select the Networking tab. Under This
connection uses the following items, select Internet
Protocol Version 4 (TCP/IPv4) or Internet Protocol Version 6 (TCP/IPv6)
and then click Properties. - 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. - Click OK.
- 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. - Replace those addresses with the IP addresses of the Google
DNS
servers:- For IPv4: 8.8.8.8 and/or 8.8.4.4.
- For IPv6: 2001:4860:4860::8888 and/or 2001:4860:4860::8844
- Restart the connection you selected in step 3.
- Test that your setup is working correctly; see Testing your new settings
below. - Repeat the procedure for additional network connections you
want to change.
Mac OS X
DNS settings are specified in the Network
window.
Example: Changing DNS server settings on Mac OS 10.5
- From the Apple menu, click System
Preferences, then click Network. - 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. - Select the connection for which you want to configure
Google Public DNS. For example:- To change the settings for an Ethernet connection,
select Built-In Ethernet, and
click Advanced. - To change the settings for a wireless connection,
select Airport, and click Advanced.
- To change the settings for an Ethernet connection,
- Select the DNS tab.
- Click + to replace any listed addresses with, or add, the
Google IP
addresses at the top of the list:- For IPv4: 8.8.8.8 and/or 8.8.4.4.
- For IPv6: 2001:4860:4860::8888 and/or 2001:4860:4860::8844
- Click Apply and OK.
- Test that your setup is working correctly; see Testing your new settings
below. - Repeat the procedure for additional network connections you
want to change.
Linux
In most modern Linux distributions, DNS settings are
configured through Network Manager.
Example: Changing DNS server settings on Ubuntu
- In the System menu, click Preferences,
then click Network Connections. - 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.
appears, select the IPv4 Settings or IPv6 Settings tab.
open the dropdown and select Automatic (DHCP) addresses only
instead. If the method is set to something else, do not change it.
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
are prompted for a password or confirmation, type the password or
provide confirmation.
below.
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
- Edit /etc/resolv.conf:
sudo vi /etc/resolv.conf - If any
nameserver
lines appear,
write down the IP addresses for future reference. - Replace the
nameserver
lines
with, or add, the following lines:For IPv4:
nameserver 8.8.8.8
nameserver 8.8.4.4For IPv6:
nameserver 2001:4860:4860::8888
nameserver 2001:4860:4860::8844 - Save and exit.
- Restart any Internet clients you are using.
- Test that your setup is working correctly; see Testing your new settings
below.
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
- Back up /etc/resolv.conf:
sudo cp /etc/resolv.conf /etc/resolv.conf.auto - Edit /etc/dhcp3/dhclient.conf:
sudo vi /etc/dhcp3/dhclient.conf - If there is a line containing
domain-name-servers
,
write down the IP addresses for future reference. - 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;
- Save and exit.
- Restart any Internet clients you are using.
- Test that your setup is working correctly; see Testing your new settings
below.
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.
Note: Some ISPs
hard-code their DNS
servers into the equipment they provide; if you are using such
a device,
you will not be able to configure it to use Google Public DNS. Instead,
you can configure each of the computers connected to the router, as
described above.
To change your settings on a router:
- In your browser, enter the IP address to access the
router's administration console. - When prompted, enter the password to access network
settings. - Find the screen in which DNS server settings are
specified. - If there are IP addresses specified in the fields for the
primary and seconday DNS servers, write them down for future reference. - 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
- Save and exit.
- Restart your browser.
- Test that your setup is working correctly; see Testing your new settings
below.
Mobile or other devices
DNS servers are typically specified under advanced wi-fi
settings. However, as every mobile device uses a different user
interface for configuring DNS server settings, we provide only a
generic procedure below. For more
information, please consult your mobile
provider's documentation.
To change your settings on a mobile device:
- Go to the screen in which wi-fi settings are
specified. - Find the screen in which DNS server settings are
specified. - If there are IP addresses specified in the fields for the
primary and seconday DNS servers, write them down for future reference. - 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
- Save and exit.
- Test that your setup is working correctly; see Testing your new settings
below.
Testing your new settings
To test that the Google DNS resolver is working:
- 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. - From your browser, type in a fixed IP address. You can
usehttp://18.62.0.96/
(which points to the websitehttp://www.eecs.mit.edu/
) as
the URL.*
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. - 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.
* Google thanks MIT for granting permission to use
this URL for the purposes of testing web connectivity.
Diagnosing resolution problems
If you are encountering problems when resolving particular
names,
and want to verify whether the problem is with Google Public DNS,
please try running the following diagnostic procedures. If you want to
report a problem to the Google
Public DNS user
group, please copy and paste the results of the commands in
your email.
This information is vital to help us to identify the cause of the
problem.
Step 1: Check to see if the authoritative nameservers are
correct
If Google Public DNS (or any open resolver) has trouble resolving a
site, or returns inconsistent answers, sometimes it is because the
authoritative nameservers are having trouble.
There are various tools and sites to help you check this.
Some users (and Google Public DNS engineers) have
found intoDNS very helpful.
For example, if you have trouble visiting www.example.com
,
visit intodns.com and
enter example.com
(the domain for www.example.com
),
or visit
http://intodns.com/example.com
directly.
Additionally, DNSViz is useful
for diagnosing DNSSEC related issues.
For example, visit dnsviz.net and
enter example.com
(the domain for www.example.com
),
or visit
http://dnsviz.net/d/example.com/dnssec/
directly.
If these tools identify a nameserver configuration issue,
please contact the owner of the nameserver to fix it.
If none of these tools finds any issue with the nameserver,
continue to step 2.
Step 2: Verify that your client can communicate with the
Google Public DNS servers
IPv4
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 the final hop, or if there are significant timeouts, there may be a network
problem preventing you
from contacting our servers. Please include the output of the command
in any communication with the Google Public DNS team.
If the last line of the output does list 8.8.8.8 as the final
hop, continue to step 3.
IPv6
Open a command prompt, and run the following command:
On Windows
tracert -d 2001:4860:4860::8888
On Mac OS X
/usr/sbin/traceroute6 -n -w 2 -q 2 -m 30 2001:4860:4860::8888
On Linux
sudo traceroute -n -w 2 -q 2 -m 30 2001:4860:4860::8888
If the last line of the output does not list 2001:4860:4860::8888
as the final hop, or if there are significant timeouts, there may be a network
problem preventing you
from contacting our servers. Try configuring Google Public DNS for IPv4 to diagnose whether
the problem is due to IPv6 connectivity on your network. If IPv4 works for you, you may want to
revert your IPv6 configuration and use Google Public DNS with IPv4 exclusively.
Otherwise, please include the output of the command
in any communication with the Google Public DNS team.
If the last line of the output does list 2001:4860:4860::8888 as the final
hop, continue to step 3.
Step 3: Verify that Google Public DNS can resolve the
selected hostname
In the following steps, replace www.example.com.
with the name that you had difficulty resolving.
(Put a period at the end of the name to avoid problems with
domain suffixes and search lists.)
IPv4
At the command prompt, run the following command:
On Windows
nslookup -debug www.example.com. 8.8.8.8
On Mac and Linux
dig @8.8.8.8 www.example.com.
If the output shows an answer section with an A record for
the
hostname, then Google Public DNS is able to resolve the name. Check
your settings to make sure your system is correctly configured to use
Google Public DNS. If you are still unable to solve the problem, please
include the output of the command in any communication with the Google
Public DNS team.
If the output does not show an answer for the hostname,
continue to step 4.
IPv6
At the command prompt, run the following command:*
On Windows
nslookup -debug -type=AAAA www.example.com. 2001:4860:4860::8888
On Mac and Linux
dig @2001:4860:4860::8888 www.example.com. AAAA
If the output shows an answer section with an AAAA record for
the hostname, then Google Public DNS is able to resolve the name. Check
your settings to make sure your system is correctly configured to use
Google Public DNS. If you are still unable to solve the problem, please
include the output of the command in any communication with the Google
Public DNS team.
If the output shows an answer section with an A (IPv4) record for the hostname,
then Google Public DNS is able to resolve the name, but the host and/or its
nameserver
are not configured to return IPv6 results. If you want to verify that you are
correctly receiving AAAA records, you can use the hostname
ipv6.google.com
as a
generic test.
If the output for ipv6.google.com
,
or another host for which you are certain
IPv6 records exist, does not show an answer,
continue to step 4.
* Note: Google properties will not return AAAA records
for all users.
Please see the
Google over IPv6
page for more
information about whether your system qualifies.
Step 4: Verify that Google Public DNS can resolve the
selected hostname without performing DNSSEC validation
Google Public DNS performs DNSSEC validation for all DNS queries by default.
When a nameserver fails DNSSEC validation, Google Public DNS returns SERVFAIL.
To verify whether Google Public DNS can resolve the hostname without performing
DNSSEC validation, run the following command:
On Windows
Unfortunately, nslookup
does not support DNSSEC
and cannot help diagnosis here.
Continue to step 5.
On Mac and Linux
IPv4
dig @8.8.8.8 www.example.com. +cd
IPv6
dig @2001:4860:4860::8888 www.example.com. AAAA +cd
If you cannot get a successful result without DNSSEC validation either,
continue to step 5.
If you get a successful result,
this usually indicates a DNSSEC misconfiguration at the nameserver.
Please make sure that you have followed through step 1.
If none of the tools finds any issue with the nameserver,
continue to step 5.
Step 5: Verify that another open resolver can resolve the
selected hostname
At the command prompt, run one of the following commands:
On Windows
nslookup www.example.com. 4.2.2.1
nslookup www.example.com. 4.2.2.2
nslookup www.example.com. 208.67.222.222
nslookup www.example.com. 208.67.220.220
On Mac and Linux
dig www.example.com. @4.2.2.1
dig www.example.com. @4.2.2.2
dig www.example.com. @208.67.222.222
dig www.example.com. @208.67.220.220
(The first two commands test Level 3's DNS servers. The last
two commands test OpenDNS's DNS servers.)
If you are unable to get a successful result, this means
that there is most likely a problem with the server you are trying to
contact. Wait some time and try running the tests again. This may be a
temporary problem
on the server's side that will likely resolve itself eventually. If it
does not, you should contact the owner of the server.
If you are able to get a successful result,
there may be a problem with Google Public DNS.
Please follow the directions here
to report an issue to the Google Public DNS team,
and include the output of the commands you ran in the report.
Switching 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.
Oh and just as a reminder
Most (if not all) UNIX implementations follow the resolv.conf convention mentioned for Linux servers. So for us sad Solaris 10/HP-UX/AIX users that is the way to go.
Gulp!
Thankfully, I can still access it.
Angharad