Disconnecting VPN breaks DNS [solved]

[zebbeman]

Hi,
When I disconnect my VPN, the original DNS is not restored, leaving me with no DNS (can only access IP addresses and hosts configured domains) . I have this issue with 19.0 and 19.1. The fast fix is to disconnect my Ethernet and reconnect. Does anyone know why this is happening?

I have a "normal" Ethernet with static IP, GW, and DNS.

My VPN is PPTP "Automatic (VPN)".

[mrmajik45]

Use https://1.1.1.1 DNS. (Until we give a fix or you're satisfied.)

[zebbeman]

I cannot type letters (https) in the dns field - is that what you meant?

[mrmajik45]

Click the link. And click on Linux for setting up the DNS. It's basically a DNS with VPN built in.
Direct steps: https://developers.cloudflare.com/1.1.1 ... 1.1/linux/

[zebbeman]

I do not want to change DNS, is that what you are suggesting? How would that change the fact that the DNS is not restored after disconnecting the VPN?

[mrmajik45]

I mean you can use a DNS which hides your IP. Until someone more tech savvy here can help.

[zebbeman]

Aah, got it, it is not that kind of VPN Thanks for the tip though

[mrmajik45]

What are you using it for?

[nina22]

change the fact that the DNS is not restored after disconnecting the VPN?

[EdgarNo]

What VPN provider are you using? Has it been updated recently? Might be a bug in some recent fix and a question for their customer support. The DNS can be cashed in browser too, try turning different browser on after turning VPN off and check if the problem still there.

[zebbeman]

It is a private PPTP and it works with mint 17.3 (and a bunch of other client computers) but not in mint 19.0/19.1.

It is not a browser issue, since I cannot ping/access fqdn, unless locally configured, after disconnecting the PPTP VPN client.

I can disconnect from an OpenVPN connection so I have this issue with PPTP only.

[GamesBond]

Having the same issue when I use PPTP but also when using L2TP over IPSEC, somehow Mint doesn't restore / reload the orignal settings for DNS. Indeed disabling WiFi and re-enabling is the quick fix but it's a little annoying bug. Bug confirmed on 5 different LM 19 / 19.1 machines.

[dkosovic]

I believe this is related to Ubuntu bug LP: 1778946 which breaks DNS resolution after disconnecting VPN connections, but only VPN clients that use pppd such as nm-pptp and nm-l2tp.

A workaround is to install the resolvconf package :
sudo apt install resolvconf

If you are using network-manager-l2tp, I would recommend using the latest version from the following PPA:

• https://launchpad.net/~nm-l2tp/+archive ... nager-l2tp

which has a number of bug fixes and enhancements.

[thierrite]

Maybe a bit 'off topic', but IPv6 and PPTP shall not be recommended for VPN from what I've read.

Also, once VPN is disconected if preferable you get fully disconnected to avoid your real IP to go into the wild.
I've read few things here (not yet fully tested), which basically show you how to configure IPtable rules to have a 'kill switch' once your VPN connection fails:
http://forums.debian.net/viewtopic.php?t=108381
and
https://linuxconfig.org/how-to-create-a ... s-on-linux

First link is a longer post, with more details provided by one guy, M51, with great details.

[zebbeman]

Thanks dkosovic! resolvconf did the trick!

As GamesBond said, L2TP behaves the same way.

Thanks for the tips thierrite, I do not use ipv6. Also, I am not using VPN for hiding, I am accessing private networks, you know the original purpose of VPN

Note: It does not go away upon upgrades, it has the same behaviour in 19, 19.1, 19.2, 19.3

Thanks!