I had the same problem and just found out that it was caused by a USB network interface that probably has been added when I plugged in a USB network device some time ago. The device has not been connected for months, yet apparently it's active in network manager, trying to get DHCP leases, which of course will fail.
Removing the USB connection profile from network manager solved the problem for me. Sylog output example before removing connection profile: Aug 31 07:59:43 p4t-nb-199 dhclient[31345]: DHCPDISCOVER on enp0s20f0u3c2 to 255.255.255.255 port 67 interval 5 (xid=0x5dc07171) Aug 31 07:59:48 p4t-nb-199 dhclient[31345]: DHCPDISCOVER on enp0s20f0u3c2 to 255.255.255.255 port 67 interval 13 (xid=0x5dc07171) Aug 31 08:00:01 p4t-nb-199 dhclient[31345]: DHCPDISCOVER on enp0s20f0u3c2 to 255.255.255.255 port 67 interval 16 (xid=0x5dc07171) Aug 31 08:00:17 p4t-nb-199 dhclient[31345]: DHCPDISCOVER on enp0s20f0u3c2 to 255.255.255.255 port 67 interval 13 (xid=0x5dc07171) Aug 31 08:00:24 p4t-nb-199 NetworkManager[1026]: <warn> [1535695224.9894] dhcp4 (enp0s20f0u3c2): request timed out Aug 31 08:00:24 p4t-nb-199 NetworkManager[1026]: <info> [1535695224.9895] dhcp4 (enp0s20f0u3c2): state changed unknown -> timeout Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <info> [1535695225.0064] dhcp4 (enp0s20f0u3c2): canceled DHCP transaction, DHCP client pid 31345 Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <info> [1535695225.0066] dhcp4 (enp0s20f0u3c2): state changed timeout -> done Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <info> [1535695225.0083] device (enp0s20f0u3c2): state change: ip-config -> failed (reason 'ip-config-unavailable', sys-iface-state: 'managed') Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <warn> [1535695225.0122] device (enp0s20f0u3c2): Activation: failed for connection 'Wired connection 1' Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <info> [1535695225.0160] device (enp0s20f0u3c2): state change: failed -> disconnected (reason 'none', sys-iface-state: 'managed') Aug 31 08:00:25 p4t-nb-199 avahi-daemon[1009]: Withdrawing address record for fe80::dc1a:366d:4591:9ef8 on enp0s20f0u3c2. Aug 31 08:00:25 p4t-nb-199 avahi-daemon[1009]: Leaving mDNS multicast group on interface enp0s20f0u3c2.IPv6 with address fe80::dc1a:366d:4591:9ef8. Aug 31 08:00:25 p4t-nb-199 systemd-timesyncd[793]: Network configuration changed, trying to establish connection. Aug 31 08:00:25 p4t-nb-199 avahi-daemon[1009]: Interface enp0s20f0u3c2.IPv6 no longer relevant for mDNS. Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <info> [1535695225.0415] policy: auto-activating connection 'Wired connection 1' Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <info> [1535695225.0441] device (enp0s20f0u3c2): Activation: starting connection 'Wired connection 1' (469a98cb-89f1-384c-bae1-f72617a41bff) Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <info> [1535695225.0446] device (enp0s20f0u3c2): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'managed') Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <info> [1535695225.0457] device (enp0s20f0u3c2): state change: prepare -> config (reason 'none', sys-iface-state: 'managed') Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <info> [1535695225.0470] device (enp0s20f0u3c2): state change: config -> ip-config (reason 'none', sys-iface-state: 'managed') Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <info> [1535695225.0475] dhcp4 (enp0s20f0u3c2): activation: beginning transaction (timeout in 45 seconds) Aug 31 08:00:25 p4t-nb-199 systemd-timesyncd[793]: Synchronized to time server 91.189.94.4:123 (ntp.ubuntu.com). Aug 31 08:00:25 p4t-nb-199 NetworkManager[1026]: <info> [1535695225.0532] dhcp4 (enp0s20f0u3c2): dhclient started with pid 31373 Aug 31 08:00:25 p4t-nb-199 dhclient[31373]: DHCPDISCOVER on enp0s20f0u3c2 to 255.255.255.255 port 67 interval 3 (xid=0x3463f46) Aug 31 08:00:26 p4t-nb-199 avahi-daemon[1009]: Joining mDNS multicast group on interface enp0s20f0u3c2.IPv6 with address fe80::dc1a:366d:4591:9ef8. Aug 31 08:00:26 p4t-nb-199 avahi-daemon[1009]: New relevant interface enp0s20f0u3c2.IPv6 for mDNS. Aug 31 08:00:26 p4t-nb-199 systemd-networkd[794]: enp0s20f0u3c2: Gained IPv6LL Aug 31 08:00:26 p4t-nb-199 avahi-daemon[1009]: Registering new address record for fe80::dc1a:366d:4591:9ef8 on enp0s20f0u3c2.*. Aug 31 08:00:26 p4t-nb-199 systemd-timesyncd[793]: Network configuration changed, trying to establish connection. Aug 31 08:00:26 p4t-nb-199 systemd-timesyncd[793]: Synchronized to time server 91.189.94.4:123 (ntp.ubuntu.com). -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to network-manager in Ubuntu. https://bugs.launchpad.net/bugs/1767322 Title: "Activation of network connection failed" popup shows incessantly Status in linux package in Ubuntu: Incomplete Status in network-manager package in Ubuntu: Confirmed Bug description: All network connections work normally, however the popup "Activation of network connection failed" keeps showing. ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: network-manager 1.10.6-2ubuntu1 ProcVersionSignature: Ubuntu 4.15.0-20.21-lowlatency 4.15.17 Uname: Linux 4.15.0-20-lowlatency x86_64 ApportVersion: 2.20.9-0ubuntu7 Architecture: amd64 CurrentDesktop: ubuntu:GNOME Date: Fri Apr 27 20:04:56 2018 IfupdownConfig: # interfaces(5) file used by ifup(8) and ifdown(8) auto lo iface lo inet loopback InstallationDate: Installed on 2018-04-03 (24 days ago) InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180402) IpRoute: default via 192.168.1.1 dev wlp2s0 proto dhcp metric 600 169.254.0.0/16 dev virbr1 scope link metric 1000 linkdown 192.168.1.0/24 dev wlp2s0 proto kernel scope link src 192.168.1.128 metric 600 192.168.100.0/24 dev virbr1 proto kernel scope link src 192.168.100.1 linkdown 192.168.122.0/24 dev virbr0 proto kernel scope link src 192.168.122.1 linkdown NetworkManager.state: [main] NetworkingEnabled=true WirelessEnabled=true WWANEnabled=true SourcePackage: network-manager UpgradeStatus: No upgrade log present (probably fresh install) nmcli-nm: RUNNING VERSION STATE STARTUP CONNECTIVITY NETWORKING WIFI-HW WIFI WWAN-HW WWAN running 1.10.6 connected started full enabled enabled enabled enabled enabled To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1767322/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
