Bounty: 100
Is there a way to prioritize a particular DNS server only when connecting to a VPN (OpenVPN) through Network Manager or one of its configuration files?
I have a VPN (192.168.1.*) I frequently connect to that has DNS (192.168.1.53) configured to resolve host names of the form *.internal.example.com on its network. My local router (192.168.0.1) has DD-WRT on it with Google’s DNS setup (those aren’t strictly needed).
I’ve replaced the systemd /etc/resolv.conf stub with a symlink to /run/systemd/resolve/resolv.conf so that host names will actually resolve using the VPN’s DNS server. Yesterday it was working fine because the VPN’s DNS server was at the top of the list.
# /etc/resolv.conf -> /run/systemd/resolve/resolv.conf
# This file is managed by man:systemd-resolved(8). Do not edit.
# ...
nameserver 192.168.1.53
nameserver 192.168.0.1
nameserver 8.8.8.8
# Too many DNS servers configured, the following entries may be ignored.
nameserver 8.8.4.4
search Home internal.example.com
However, when I connected today the DNS entries were reordered.
# /etc/resolv.conf -> /run/systemd/resolve/resolv.conf
# This file is managed by man:systemd-resolved(8). Do not edit.
# ...
nameserver 192.168.0.1
nameserver 8.8.8.8
nameserver 8.8.4.4
# Too many DNS servers configured, the following entries may be ignored.
nameserver 192.168.1.53
search Home internal.example.com
The order frequently changes after a reboot. Sometimes upon reconnection to the VPN I notice the order changes (after experiencing the resolution issue).
systemd-resolve works just fine and can resolve the hosts using the proper DNS server.
$ systemd-resolve --status --no-pager
Global
DNSSEC NTA: ...
Link 10 (tun0)
Current Scopes: DNS
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
DNS Servers: 192.168.1.53
DNS Domain: internal.example.com
Link 2 (eno1)
Current Scopes: DNS
LLMNR setting: yes
MulticastDNS setting: no
DNSSEC setting: no
DNSSEC supported: no
DNS Servers: 192.168.0.1
8.8.8.8
8.8.4.4
192.168.1.53
DNS Domain: Home
$ systemd-resolve srv1.internal.example.com
srv1.internal.example.com: 192.168.1.113
-- Information acquired via protocol DNS in 2.1ms.
-- Data is authenticated: no
ping, nslookup, and ssh all fail though.
$ ping srv1.internal.example.com
ping: srv1.internal.example.com: Name or service not known
$ nslookup srv1.internal.example.com
Server: 192.168.0.1
Address: 192.168.0.1#53
** server can't find srv1.internal.example.com: NXDOMAIN
$ ssh srv1.internal.example.com
ssh: Could not resolve hostname srv1.internal.example.com: Name or service not known
A few notes.
I connect to the VPN through Network Manager. I have the VPN’s DNS manually specified on the VPN under: IPv4 > DNS Servers.
I tried using a separate wired ethernet connection configured with the VPN’s DNS under: IPv4 > Other DNS Servers.