Problem resolving many web pages

Solution 1:

Part 1 - PPPoE connection not working

I would try disabling the Network Manager and configuring the network manually like explained in Ubuntu help ADSLPPPoE. Use the Config with pppoeconf part first which is basically running sudo pppoeconf and answering the questions. As you need to use a different DNS server than the one of your ISP, answer no to the question about using the peer DNS server.

Optional if your internet connection is not restarted at boot: You can edit nano /etc/rc.local, add the following lines before the exit line and reboot to test it.

killall pppd
ifconfig eth0 up
pon dsl-provider

Network manager won't be used when you use the manual config but you can disable it clicking on it and de-selecting the option enable network (and enable wireless if present). If disabling only doesnt work, you can also uninstall it with sudo apt-get remove network-manager and after sudo apt-get autoremove to clean the auto-installed packages.

Part 2 Changing default ISP DNS server to openDNS

I found here that the best way to use a static DNS with resolvconf is to add the nameserver in /etc/network/interfaces or to add it in /etc/resolvconf/resolv.conf.d/head. As your interfaces are automatically configured (dhcp) you have to use the head file:

sudo nano /etc/resolvconf/resolv.conf.d/head

and add at the end:

nameserver 208.67.222.222
nameserver 208.67.220.220

Limitations

You cannot use Network-Manager to connect. However, this automatically gets you connected to the internet. Otherwise, you can connect by running pon dsl-provider. To disconnect, you need to be sudo, so running sudo poff disconnects.
[This issue is only with Ubuntu 12.04.] While Booting Ubuntu (with Modem turned off or while it is still trying to establish a link with the ISP) - Ubuntu waits for loading Network-Configuration for about 2 mins and thereafter boots without Network-Configuration. To get online you have to run pon dsl-provider.

Fixes to remove the previous tests made (not needed in other cases):

As we deleted the resolv.conf symlink before, we need to recreate it (not needed on new install):

cd /etc
sudo rm resolv.conf
sudo ln -s ../run/resolvconf/resolv.conf /etc/resolv.conf

If this works, you can revert the changes in /etc/dhcp/dhclient.conf we made before.

Solution 2:

Verify that your client can communicate with the openDNS servers
```
sudo traceroute -n -w 2 -q 2 -m 30  208.67.222.222
```
If the last line of the output does not list 208.67.222.222 as the final hop, or if there are significant timeouts, there may be a network problem preventing you from contacting openDNS servers.
Verify that openDNS can resolve the selected hostname
```
dig @208.67.222.222 www.difficult.com.      
```
At the command prompt, run the following command, replacing www.difficult.com. with the name that you were having difficulty resolving (putting a period at the end of the name to avoid problems with domain suffixes and search lists)

If the output does not show an answer for the hostname, continue:
Verify that another open resolver can resolve the selected hostname
```
dig @8.8.8.8 www.difficult.com.
dig @8.8.8.4 www.difficult.com.
dig @4.2.2.1 www.difficult.com.
dig @4.2.2.2 www.difficult.com.
```
If you do get a successful result, there may be a problem with openDNS
Check to see if the authoritative nameservers are correct

intoDNS is very helpful.

UPDATE:
This answer could not deal with the problem , just for troubleshooting.
If DNS resolve worked fine,go to see laurent's answer furthermore.

Reference:public DNS troubleshooting

Solution 3:

Append this line to you /etc/resolv.conf:

nameserver 8.8.8.8

Solution 4:

The original problem could possibly have been solved by doing the following.

sudo apt-get install resolvconf
sudo dpkg-reconfigure resolvconf

Solution 5:

Maybe you can try disabling the dnsmasq:

sudo vim /etc/NetworkManager/NetworkManager.conf

Put a # in front of dns=dnsmasq

Then:

sudo restart network-manager

I have a problem of resolving some websites after I installed 12.04 and 12.10. After I disabled dnsmasq everything worked fine.

If this helps, you can then install the full dnsmasq service and put your favourite DNS provider in /etc/resolvconf/resolv.conf.d/tail.