I am seeing the same problem on a physical host running Linux Mint. I too have found that clicking the network icon to toggle it off and back on can restore connections. Additionally, I have found that the connection may be restored without intervention, given sufficient time (potentially hours). Sorry that this is a long post - when trying to add an attachment, the U.R.L. was not found. I have tried to provide anything that may be relevant. The connection was lost at 03:57:51, and regained at 04:24. The computers featured are yoyo, 192.168.42.187, 00:25:64:72:72:14, the Linux Mint computer, and kevin, 192.168.42.129, 00:50:04:23:f7:80, the D.H.C.P. server and Internet gateway. [LinuxMint] graham@yoyo $ cat /etc/network/interfaces # interfaces(5) file used by ifup(8) and ifdown(8) auto lo iface lo inet loopback Tue Aug 22 17:57:47 ~ [LinuxMint] graham@yoyo $ lspci | grep -i "net" 09:00.0 Ethernet controller: Marvell Technology Group Ltd. 88E8040 PCI-E Fast Ethernet Controller (rev 13) 0c:00.0 Network controller: Broadcom Corporation BCM4312 802.11b/g LP-PHY (rev 01) Tue Aug 22 17:59:23 ~ The Broadcom wireless adaptor is not active. [LinuxMint] graham@yoyo $ cat /etc/os-release NAME="Linux Mint" VERSION="18 (Sarah)" ID=linuxmint ID_LIKE=ubuntu PRETTY_NAME="Linux Mint 18" VERSION_ID="18" HOME_URL="http://www.linuxmint.com/" SUPPORT_URL="http://forums.linuxmint.com/" BUG_REPORT_URL="http://bugs.launchpad.net/linuxmint/" UBUNTU_CODENAME=xenial Tue Aug 22 17:48:57 ~ [LinuxMint] graham@yoyo $ uname -a Linux yoyo 4.4.0-21-generic #37-Ubuntu SMP Mon Apr 18 18:33:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux Tue Aug 22 18:04:00 ~ Here is a excerpt from kern.log, showing that the D.H.C.P. lease was not renewed and the network connection was lost:- Aug 21 03:00:30 yoyo NetworkManager[1049]: [1503280830.6457] dhcp4 (eth0): state changed bound -> bound Aug 21 03:13:25 yoyo NetworkManager[1049]: [1503281605.4009] address 192.168.42.187 Aug 21 03:13:25 yoyo NetworkManager[1049]: [1503281605.4009] plen 25 (255.255.255.128) Aug 21 03:13:25 yoyo NetworkManager[1049]: [1503281605.4010] gateway 192.168.42.129 Aug 21 03:13:25 yoyo NetworkManager[1049]: [1503281605.4010] server identifier 192.168.42.129 Aug 21 03:13:25 yoyo NetworkManager[1049]: [1503281605.4010] lease time 1800 Aug 21 03:13:25 yoyo NetworkManager[1049]: [1503281605.4010] nameserver '192.168.42.129' Aug 21 03:13:25 yoyo NetworkManager[1049]: [1503281605.4011] nameserver '192.168.42.248' Aug 21 03:13:25 yoyo NetworkManager[1049]: [1503281605.4011] domain name 'example.net' Aug 21 03:13:25 yoyo NetworkManager[1049]: [1503281605.5497] dhcp4 (eth0 ): state changed bound -> bound Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5210] address 192.168.42.187 Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5211] plen 25 (255.255.255.128) Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5211] gateway 192.168.42.129 Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5211] server identifier 192.168.42.129 Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5212] lease time 1800 Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5212] nameserver '192.168.42.129' Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5212] nameserver '192.168.42.248' Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5212] domain name 'example.net' Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5213] dhcp4 (eth0): state changed bound -> bound Aug 21 04:00:55 yoyo kernel: [2364015.580056] nfs: server gerald not responding, timed out Aug 21 04:03:55 yoyo kernel: [2364195.804051] nfs: server gerald not responding, timed out Here is a (slightly edited) excerpt from the same period in syslog:- Aug 21 03:27:48 yoyo dhclient[6325]: DHCPREQUEST of 192.168.42.187 on eth0 to 192.168.42.129 port 67 (xid=0x4ce954e5) Aug 21 03:27:48 yoyo dhclient[6325]: DHCPACK of 192.168.42.187 from 192.168.42.129 Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5210] address 192.168.42.187 Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5211] plen 25 (255.255.255.128) Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5211] gateway 192.168.42.129 Aug 21 03:27:49 yoyo dhclient[6325]: bound to 192.168.42.187 -- renewal in 868 seconds. Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5211] server identifier 192.168.42.129 Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5212] lease time 1800 Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5212] nameserver '192.168.42.129' Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5212] nameserver '192.168.42.248' Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5212] domain name 'example.net' Aug 21 03:27:49 yoyo NetworkManager[1049]: [1503282469.5213] dhcp4 (eth0): state changed bound -> bound Aug 21 03:27:49 yoyo dbus[999]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedes ktop.nm-dispatcher.service' Aug 21 03:27:50 yoyo systemd[1]: Starting Network Manager Script Dispatcher Service... Aug 21 03:27:50 yoyo dbus[999]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher' Aug 21 03:27:50 yoyo systemd[1]: Started Network Manager Script Dispatcher Service. Aug 21 03:27:50 yoyo nm-dispatcher: req:1 'dhcp4-change' [eth0]: new request (1 scripts) Aug 21 03:27:50 yoyo nm-dispatcher: req:1 'dhcp4-change' [eth0]: start running ordered scripts... Aug 21 03:34:01 yoyo CRON[1817]: (root) CMD (/usr/local/bin/enat-jobs/enat.MemStats /root/.enat/last.enat.MemStats) Aug 21 03:34:01 yoyo MemStats: Memory used: 3005504KiB (75.01%), swap used: 1759248KiB (21.97%), loads: 2.19, 1.89, 1.92, net: 383 B/s in, 222 B/s out Aug 21 03:42:17 yoyo dhclient[6325]: DHCPREQUEST of 192.168.42.187 on eth0 to 192.168.42.129 port 67 (xid=0x4ce954e5) Aug 21 03:42:17 yoyo dhclient[6325]: DHCPACK of 192.168.42.187 from 192.168.42.129 Aug 21 03:42:18 yoyo dhclient[6325]: bound to 192.168.42.187 -- renewal in 728 seconds. Aug 21 03:54:25 yoyo dhclient[6325]: DHCPREQUEST of 192.168.42.187 on eth0 to 192.168.42.129 port 67 (xid=0x4ce954e5) Aug 21 03:54:25 yoyo dhclient[6325]: DHCPACK of 192.168.42.187 from 192.168.42.129 Aug 21 03:54:26 yoyo dhclient[6325]: bound to 192.168.42.187 -- renewal in 775 seconds. Aug 21 03:57:50 yoyo avahi-daemon[1017]: Withdrawing address record for 192.168.42.187 on eth0. Aug 21 03:57:50 yoyo rsyslogd-2359: action 'action 18' resumed (module 'builtin:omfwd') [v8.16.0 try http://www.rsyslog.com/e/2359 ] Aug 21 03:57:50 yoyo avahi-daemon[1017]: Leaving mDNS multicast group on interface eth0.IPv4 with address 192.168.42.187. Aug 21 03:57:50 yoyo avahi-daemon[1017]: Interface eth0.IPv4 no longer relevant for mDNS. Aug 21 03:57:51 yoyo ntpd[6912]: Deleting interface #3 eth0, 192.168.42.187#123, interface stats: received=1649, sent=1923, dropped=0, active_time=88923 secs Aug 21 03:57:51 yoyo ntpd[6912]: 178.62.250.107 local addr 192.168.42.187 -> Aug 21 03:57:51 yoyo ntpd[6912]: 134.0.16.1 local addr 192.168.42.187 -> Later, the connection was discovered again (syslog):- Aug 21 04:20:06 yoyo dhclient[6325]: dhclient.c:2386: Failed to send 300 byte long packet over fallback interface. Aug 21 04:20:23 yoyo dhclient[6325]: DHCPREQUEST of 192.168.42.187 on eth0 to 192.168.42.129 port 67 (xid=0x4ce954e5) Aug 21 04:20:23 yoyo dhclient[6325]: send_packet: Network is unreachable Aug 21 04:20:23 yoyo dhclient[6325]: send_packet: please consult README file regarding broadcast address. Aug 21 04:20:23 yoyo dhclient[6325]: dhclient.c:2386: Failed to send 300 byte long packet over fallback interface. Aug 21 04:20:41 yoyo dhclient[6325]: DHCPREQUEST of 192.168.42.187 on eth0 to 255.255.255.255 port 67 (xid=0x4ce954e5) Aug 21 04:22:25 yoyo kernel: [2365305.788044] nfs: server gerald not responding, timed out Aug 21 04:22:30 yoyo kernel: [2365310.796047] nfs: server gerald not responding, timed out Aug 21 04:24:19 yoyo dhclient[6325]: message repeated 17 times: [ DHCPREQUEST of 192.168.42.187 on eth0 to 255.255.255.255 port 67 (xid=0x4ce954e5)] Aug 21 04:24:27 yoyo dhclient[6325]: DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 3 (xid=0xb9ab7008) Aug 21 04:24:27 yoyo dhclient[6325]: DHCPREQUEST of 192.168.42.187 on eth0 to 255.255.255.255 port 67 (xid=0x870abb9) Aug 21 04:24:27 yoyo dhclient[6325]: DHCPOFFER of 192.168.42.187 from 192.168.42.129 Aug 21 04:24:27 yoyo rsyslogd-2359: message repeated 9 times: [action 'action 18' resumed (module 'builtin:omfwd') [v8.16.0 try http ://www.rsyslog.com/e/2359 ]] Aug 21 04:24:27 yoyo rsyslogd-2007: action 'action 18' suspended, next retry is Mon Aug 21 04:24:57 2017 [v8.16.0 try http://www.rsy slog.com/e/2007 ] Aug 21 04:24:27 yoyo dhclient[6325]: DHCPACK of 192.168.42.187 from 192.168.42.129 Aug 21 04:24:27 yoyo NetworkManager[1049]: [1503285867.5744] dhcp4 (eth0): state changed bound -> expire Aug 21 04:24:27 yoyo NetworkManager[1049]: [1503285867.7381] dhcp4 (eth0): canceled DHCP transaction, DHCP client pid 6325 Aug 21 04:24:27 yoyo NetworkManager[1049]: [1503285867.7381] dhcp4 (eth0): state changed expire -> done Aug 21 04:24:27 yoyo NetworkManager[1049]: [1503285867.8850] device (eth0): state change: activated -> failed (reason 'ip-co nfig-expired') [100 120 6] Aug 21 04:24:27 yoyo NetworkManager[1049]: [1503285867.9286] manager: NetworkManager state is now CONNECTED_LOCAL Aug 21 04:24:27 yoyo NetworkManager[1049]: [1503285867.9290] manager: NetworkManager state is now DISCONNECTED Aug 21 04:24:28 yoyo NetworkManager[1049]: [1503285868.4069] device (eth0): Activation: failed for connection 'Wired connection 1' Aug 21 04:24:29 yoyo dbus[999]: [system] Activating via systemd: service name='org.freedesktop.nm_dispatcher' unit='dbus-org.freedesktop.nm-dispatcher.service' Aug 21 04:24:29 yoyo NetworkManager[1049]: [1503285869.8415] (pid 6325) unhandled DHCP event for interface eth0 Aug 21 04:24:29 yoyo NetworkManager[1049]: [1503285869.8420] (pid 6325) unhandled DHCP event for interface eth0 Aug 21 04:24:29 yoyo systemd[1]: Starting Network Manager Script Dispatcher Service... Aug 21 04:24:30 yoyo NetworkManager[1049]: [1503285870.0385] device (eth0): state change: failed -> disconnected (reason 'none') [120 30 0] Aug 21 04:24:30 yoyo avahi-daemon[1017]: Withdrawing address record for fe80::c1e6:4b25:5c64:f669 on eth0. Aug 21 04:24:30 yoyo avahi-daemon[1017]: Leaving mDNS multicast group on interface eth0.IPv6 with address fe80::c1e6:4b25:5c64:f669. Aug 21 04:24:30 yoyo avahi-daemon[1017]: Interface eth0.IPv6 no longer relevant for mDNS. Aug 21 04:24:30 yoyo NetworkManager[1049]: [1503285870.7254] dns-mgr: Writing DNS information to /sbin/resolvconf Aug 21 04:24:30 yoyo dnsmasq[1364]: setting upstream servers from DBus Aug 21 04:24:31 yoyo ntpd[6912]: Deleting interface #5 eth0, fe80::c1e6:4b25:5c64:f669%2#123, interface stats: received=0, sent=0, dropped=0, active_time=90523 secs Aug 21 04:24:31 yoyo dbus[999]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher' Meanwhile, from the D.H.C.P. server:- 2017-08-21T03:13:24+01:00 kevin dhcpd[3454]: DHCPREQUEST for 192.168.42.187 from 00:25:64:72:72:14 (yoyo) via enp0s19 2017-08-21T03:13:24+01:00 kevin dhcpd[3454]: DHCPACK on 192.168.42.187 to 00:25:64:72:72:14 (yoyo) via enp0s19 ... 2017-08-21T03:27:48+01:00 kevin dhcpd[3454]: DHCPREQUEST for 192.168.42.187 from 00:25:64:72:72:14 (yoyo) via enp0s19 2017-08-21T03:27:48+01:00 kevin dhcpd[3454]: DHCPACK on 192.168.42.187 to 00:25:64:72:72:14 (yoyo) via enp0s19 ... 2017-08-21T03:42:17+01:00 kevin dhcpd[3454]: DHCPREQUEST for 192.168.42.187 from 00:25:64:72:72:14 (yoyo) via enp0s19 2017-08-21T03:42:17+01:00 kevin dhcpd[3454]: DHCPACK on 192.168.42.187 to 00:25:64:72:72:14 (yoyo) via enp0s19 ... 2017-08-21T03:54:25+01:00 kevin dhcpd[3454]: DHCPREQUEST for 192.168.42.187 from 00:25:64:72:72:14 (yoyo) via enp0s19 2017-08-21T03:54:25+01:00 kevin dhcpd[3454]: DHCPACK on 192.168.42.187 to 00:25:64:72:72:14 (yoyo) via enp0s19 ... 2017-08-21T03:57:51+01:00 kevin dhcpcd[2941]: enp0s19: hardware address 00:25:64:72:72:14 claims 192.168.42.129 2017-08-21T03:57:51+01:00 kevin kernel: IPv4: martian source 192.168.42.129 from 0.0.0.0, on dev enp0s19 2017-08-21T03:57:51+01:00 kevin kernel: ll header: 00000000: 00 50 04 23 f7 80 00 25 64 72 72 14 08 00 .P.#...%drr... 2017-08-21T03:57:52+01:00 kevin kernel: IPv4: martian source 192.168.42.129 from 0.0.0.0, on dev enp0s19 2017-08-21T03:57:52+01:00 kevin kernel: ll header: 00000000: 00 50 04 23 f7 80 00 25 64 72 72 14 08 00 .P.#...%drr... 2017-08-21T03:57:56+01:00 kevin kernel: IPv4: martian source 192.168.42.129 from 0.0.0.0, on dev enp0s19 2017-08-21T03:57:56+01:00 kevin kernel: ll header: 00000000: 00 50 04 23 f7 80 00 25 64 72 72 14 08 00 .P.#...%drr... ... 2017-08-21T04:21:24+01:00 kevin kernel: IPv4: martian source 192.168.42.129 from 0.0.0.0, on dev enp0s19 2017-08-21T04:21:24+01:00 kevin kernel: ll header: 00000000: 00 50 04 23 f7 80 00 25 64 72 72 14 08 00 .P.#...%drr... 2017-08-21T04:21:26+01:00 kevin dhcpd[3454]: reuse_lease: lease age 44 (secs) under 25% threshold, reply with unaltered, existing lease for 192.168.42.187 2017-08-21T04:21:26+01:00 kevin dhcpd[3454]: DHCPREQUEST for 192.168.42.187 from 00:25:64:72:72:14 via enp0s19 2017-08-21T04:21:26+01:00 kevin dhcpd[3454]: DHCPACK on 192.168.42.187 to 00:25:64:72:72:14 via enp0s19 2017-08-21T04:21:26+01:00 kevin kernel: IPv4: martian source 192.168.42.129 from 0.0.0.0, on dev enp0s19 2017-08-21T04:21:26+01:00 kevin kernel: ll header: 00000000: 00 50 04 23 f7 80 00 25 64 72 72 14 08 00 .P.#...%drr... 2017-08-21T04:21:27+01:00 kevin kernel: IPv4: martian source 192.168.42.129 from 0.0.0.0, on dev enp0s19 ... 2017-08-21T04:21:33+01:00 kevin kernel: IPv4: martian source 192.168.42.129 from 0.0.0.0, on dev enp0s19 2017-08-21T04:21:33+01:00 kevin kernel: ll header: 00000000: 00 50 04 23 f7 80 00 25 64 72 72 14 08 00 .P.#...%drr... 2017-08-21T04:21:33+01:00 kevin sm-mta[4212]: v7L3LXQA004211: to=graham, ctladdr=