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DNS Settings on Ubuntu 14.04

rated 0 times [ 0] [ 0] / answers: 1 / hits: 1621 / 3 Years ago, sun, may 23, 2021, 5:05:22

I just upgraded on Ubuntu 14.04 because I did some nasty thing and clumsily delete configuration files on my previous Ubuntu 12.04, and now my network is not working properly.

The POP server of my mail is something like pop.univmtl.ca , it is our university mail server. When I'm outside of the university, the address of the POP server is 142.137.XXX.130, and when I am in the university it is supposed to be 10.162.XXX.162. The problem is that my mail is not working anymore everytime I connect in the local network of my university.

So I tried to ping pop.univmtl.ca -c4, then I found that the POP server is still 142.137.XXX.130 eventhough I am inside the university's local network. And when I try to change the POP settings of my mail to the IP of the POP server (10.162.XXX.162), then I can still receive my mail. But I'm not willing to change this address everytime so I was looking to troubleshoot my DNS settings.

I'm not experimented in Ubuntu and networking, but after googling I edited

sudo gedit /etc/dhcp/dhclient.conf

and added almost every DNS Server I found when I'm pinging from my tablet, here is the line:

prepend domain-name-servers 10.162.X.50, 10.162.X.51, 206.167.X13.111, 206.167.X53.111, 8.8.8.8, 8.8.4.4;

(Sorry for changing some digits to X, I don't know anything about legal issue).

What I The connection information when I open the network-manager GUI looks OK, it appears like the right DNS is used, and when I do

nmcli dev list iface wlan0 | grep IP4

I get :

IP4.DNS[1]:                             10.162.X.50

IP4.DNS[2]:                             10.162.X.51

IP4.DNS[3]:                             206.167.X13.111

IP4.DNS[4]:                             206.167.X53.111

IP4.DNS[5]:                             8.8.8.8

IP4.DNS[6]:                             8.8.4.4

IP4.WINS[1]:                            10.18.X.35

IP4.WINS[2]:                            10.18.X.37

But even with this configuration, ping pop.univmtl.ca -c4 still gives me wrong POP Server IP address. nm-tool gave me the same output as above.
Also, I tried to sudo gedit /etc/resolvconf/resolv.conf.d and comment the line dns=dnsmasq. That didn't solve the problem.

Please help me, I don't know what else to do! I tried to look for everything that can reset all the network configurations, but my problem is still there. Thank you in advance.

Andrew

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3 Years ago

answered 3 Years ago ravturtl · Accepted Answer

If you can use DHCP, do it and delete all DNS settings from the interface, let router assign you the right DNS server to your network card, if you do your settings manually in /etc/network/interfaces or else, you may configure multiple settings for one interface, wlan0 and wlan0:0, one for school and one for other, there use only the necessary DNS servers in each profile.

An easy way to see, what is supplying you with wrong IP address, use dig command against schools nameserver.

$ dig @10.162.X.50 pop.univmtl.ca

Look for A record, your primary nameserver should be the one in school with IP 10.162.XXX.162. If this is right, it means probably another nameserver is being used. Too many of nameservers does not help as first found is served, same applies for /etc/hosts.

Short term fix would be to alter /etc/hosts and add line when in school, make a script.

10.162.XXX.162 pop.univmtl.ca