Comment 4 for bug 1586570

I am seeing this with 64-bit 14.04.5 (even though 'grheard' did not have this problem with 14.04) using OpenVPN via the network manager. Seems to happen independently of DHCP renewals as several were logged before this last bit:

Feb 23 19:31:03 paul-ubuntu dhclient: DHCPREQUEST of 192.168.1.100 on eth1 to 192.168.1.1 port 67 (xid=0xacb31f1)
Feb 23 19:31:03 paul-ubuntu dhclient: DHCPACK of 192.168.1.100 from 192.168.1.1
Feb 23 19:31:03 paul-ubuntu dhclient: bound to 192.168.1.100 -- renewal in 1379 seconds.
Feb 23 19:31:03 paul-ubuntu NetworkManager[1577]: <info> (eth1): DHCPv4 state changed renew -> renew
Feb 23 19:31:03 paul-ubuntu NetworkManager[1577]: <info> address 192.168.1.100
Feb 23 19:31:03 paul-ubuntu NetworkManager[1577]: <info> prefix 24 (255.255.255.0)
Feb 23 19:31:03 paul-ubuntu NetworkManager[1577]: <info> gateway 192.168.1.1
Feb 23 19:31:03 paul-ubuntu NetworkManager[1577]: <info> hostname 'Desktop'
Feb 23 19:31:03 paul-ubuntu NetworkManager[1577]: <info> nameserver '192.168.1.1'
Feb 23 19:31:03 paul-ubuntu dbus[1306]: [system] Activating service name='org.freedesktop.nm_dispatcher' (using servicehelper)
Feb 23 19:31:03 paul-ubuntu dbus[1306]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Feb 23 19:34:32 paul-ubuntu nm-openvpn[2357]: [server] Inactivity timeout (--ping-restart), restarting
Feb 23 19:34:32 paul-ubuntu nm-openvpn[2357]: SIGUSR1[soft,ping-restart] received, process restarting
Feb 23 19:34:34 paul-ubuntu nm-openvpn[2357]: NOTE: the current --script-security setting may allow this configuration to call user-defined scripts
Feb 23 19:34:54 paul-ubuntu nm-openvpn[2357]: RESOLVE: Cannot resolve host address: <redacted>: Temporary failure in name resolution

This fault continued through several more DHCP renewals until I manually reset the link:

Feb 23 23:04:11 paul-ubuntu nm-openvpn[2357]: message repeated 502 times: [ RESOLVE: Cannot resolve host address: <redacted>: Temporary failure in name resolution]
Feb 23 23:04:26 paul-ubuntu nm-openvpn[2357]: RESOLVE: signal received during DNS resolution attempt
Feb 23 23:04:26 paul-ubuntu avahi-daemon[1439]: Withdrawing workstation service for tun0.
Feb 23 23:04:26 paul-ubuntu NetworkManager[1577]: SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/tun0, iface: tun0)

So manually disconnecting and reconnecting the VPN works, but is obviously not a satisfactory solution for machines that are normally unattended or if you wish to maintain privacy!

System details:

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.5 LTS
Release: 14.04
Codename: trusty

$ apt-cache policy openvpn
openvpn:
  Installed: 2.3.2-7ubuntu3.1
  Candidate: 2.3.2-7ubuntu3.1
  Version table:
 *** 2.3.2-7ubuntu3.1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
        500 http://security.ubuntu.com/ubuntu/ trusty-security/main amd64 Packages
        100 /var/lib/dpkg/status
     2.3.2-7ubuntu3 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages