DNS problem when connecting to a corporate VPN

[witizer]

Hello everybody.
I am running Linux Mint 18.3. I have the following problem: I successfully connect to a corporate VPN (Cisco vpn) but when this happens, I cannot load web pages as apparently the DNS addresses are not resolved correctly. Could you help me? thank you!

[greerd]

Hi witizer, welcome to the forum.

I would start by checking your nameservers.

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cat /etc/resolv.conf

You will probably have to change them to your corporate nameserver addresses.

[witizer]

Hello greerd, thank you for your answer.
This is what I get before connecting to the VPN:

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# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.1.1

And this is what I get after connecting:

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# Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8)
#     DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN
nameserver 127.0.1.1
search xxxxxx

There is an extra line added presumeby by my company.

[greerd]

Your output from /etc/resolv.conf says you're using resolvconf (not to be mistaken for the text configuration file /etc/resolv.conf) and the nameserver 127.0.1.1 indicates that you're also using dnsmasq. As opposed to using a static /etc/resolv.conf file like I use, your /etc/resolv.conf should be a system link to /run/NetworkManager/resolv.conf.

Unfortunately I'm not familiar with dnsmasq so can only give a link or two that might help, also opening a terminal and entering man dnsmasq and man resolvconf will display the manual for said commands.

What I would try first is to add your corporate supplied dns nameserver addresses to your Network Manager - Edit Connections - Connection type (wired or wireless) - IPv4 Settings - DNS Servers, save and try that.

If no luck I might try following this link that disables dnsmasq and see if the newly edited Network Manager DNS server addresses now work.

Are you using Cisco AnyConnect for Linux app? If so maybe this link and the "Humans" link included might help.

Sorry I can't be more definitive, maybe someone else has more info,
Good Luck

EDIT: When I mention dnsmasq above, I should of been explicit and indicated you probably have dnsmasq-base installed, which is part of or can be used in conjunction with Network Manager. The first link above (disabling dnsmasq) only mentions dnsmasq but it is actually talking about dnsmasq-base.

[witizer]

What I would try first is to add your corporate supplied dns nameserver addresses to your Network Manager - Edit Connections - Connection type (wired or wireless) - IPv4 Settings - DNS Servers, save and try that.

Solved using your first solution. Thank you a lot and Merry Christmas.

[greerd]

You're welcome, glad you got it sorted out.

Merry Christmas to you too!