Ubuntu – DNS-Settings on Network-Manager when using VPN

dnsnetwork-managervpnvpnc

I recently updated to 19.04 and noticed some change in NetworkManager when using VPNs.

  • I want to use a VPN with an own local DNS-server, which is pushed from DHCP
  • I have seperate VPN profiles. One for a "full VPN" which installes a default-route to the remote network, and one "split tunnel" profile, having the setting for local resources only enabled

Since i updated to 19.04, NetworkManager seems to only use the pushed DNS server, what means when the default-route is allowed to install (when checkbox "use this connection only for resources on its network") is not checked.

Let NetworkManager install a default route:

~$ resolvectl status tun0
Link 16 (tun0)
      Current Scopes: DNS
DefaultRoute setting: yes
       LLMNR setting: yes
MulticastDNS setting: no
  DNSOverTLS setting: no
      DNSSEC setting: no
    DNSSEC supported: no
  Current DNS Server: 192.168.1.1
         DNS Servers: 192.168.1.1
          DNS Domain: local.domain

activate checkbox for local resources only in the same vpn profile:

~$ resolvectl status tun0
Link 8 (tun0)
      Current Scopes: none
DefaultRoute setting: no
       LLMNR setting: yes
MulticastDNS setting: no
  DNSOverTLS setting: no
      DNSSEC setting: no
    DNSSEC supported: no

This setting was working independently from default-route-setting before, seems like it changed with new 19.04 NetworkManager (v1.16.0). Can anyone confirm?

Edit: This is a desktop installation. Here are some details:

~$ ls -al /etc/resolv.conf
lrwxrwxrwx 1 root root 39 Apr 20 15:41 /etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf

~$ cat /etc/resolv.conf
# This file is managed by man:systemd-resolved(8). Do not edit.
#
# This is a dynamic resolv.conf file for connecting local clients to the
# internal DNS stub resolver of systemd-resolved. This file lists all
# configured search domains.
#
# Run "resolvectl status" to see details about the uplink DNS servers
# currently in use.
#
# Third party programs must not access this file directly, but only through the
# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,
# replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.

nameserver 127.0.0.53
options edns0
search uman.enbw.net

~$ cat /etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

~$ cat /etc/netplan/*.yaml
# Let NetworkManager manage all devices on this system
network:
  version: 2
  renderer: NetworkManager

Best Answer

I googled here and have exactly the same issue too. (Ubuntu 19.04)

For me, this answer solved.

nmcli c modify <vpn-settings-name> ipv4.dns-search '<domain>'

You should specify <vpn-settings-name> that corresponds to a VPN setting name in GUI. And <domain> is the domain name you want to search via DNS in the remote network.

After reconnecting to VPN, systemd-resolved status ppp0 shows

Link 6 (ppp0)
      Current Scopes: DNS
DefaultRoute setting: yes
       LLMNR setting: yes
MulticastDNS setting: no
  DNSOverTLS setting: no
      DNSSEC setting: no
    DNSSEC supported: no
  Current DNS Server: 192.168.1.1
         DNS Servers: 192.168.1.1 (<--- my dns)
                      192.168.1.10
          DNS Domain: corp
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