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Since yesterday, my wired network connection has been dropping for a couple of seconds every 30 seconds or so. To my knowledge, I had not made any changes to my network.

Output of ifconfig -a:

➜  ~  ifconfig -a
eth0      Link encap:Ethernet  HWaddr 6c:f0:49:b9:b1:7f  
          inet addr:192.168.0.16  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::6ef0:49ff:feb9:b17f/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:11597 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9783 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:10101682 (10.1 MB)  TX bytes:1215142 (1.2 MB)
          Interrupt:48 Base address:0x8000 

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:96691 errors:0 dropped:0 overruns:0 frame:0
          TX packets:96691 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:13594355 (13.5 MB)  TX bytes:13594355 (13.5 MB)

lspci |grep Ethernet:

04:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 03)

Pinging my router:

➜  ~  ping 192.168.0.1
PING 192.168.0.1 (192.168.0.1) 56(84) bytes of data.
64 bytes from 192.168.0.1: icmp_seq=1 ttl=64 time=0.435 ms
64 bytes from 192.168.0.1: icmp_seq=2 ttl=64 time=0.571 ms
ping: sendmsg: Network is unreachable
ping: sendmsg: Network is unreachable
ping: sendmsg: Network is unreachable
ping: sendmsg: Network is unreachable
ping: sendmsg: Network is unreachable
64 bytes from 192.168.0.1: icmp_seq=8 ttl=64 time=1.03 ms

And the output of route:

➜  ~  route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         192.168.0.1     0.0.0.0         UG    0      0        0 eth0
192.168.0.0     *               255.255.255.0   U     1      0        0 eth0

Some messages from /var/logs/syslog:

➜  ~  tail -f /var/log/syslog 
Jun  6 10:37:34 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:37:34 lolbox dhclient: IA_NA status code NoAddrsAvail.
Jun  6 10:37:37 lolbox dnsmasq[1138]: Maximum number of concurrent DNS queries reached (max: 150)
Jun  6 10:37:37 lolbox dnsmasq[1362]: Maximum number of concurrent DNS queries reached (max: 150)
Jun  6 10:37:39 lolbox dhclient: XMT: Solicit on eth0, interval 8660ms.
Jun  6 10:37:39 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:37:39 lolbox dhclient: IA_NA status code NoAddrsAvail.
Jun  6 10:37:47 lolbox dhclient: XMT: Solicit on eth0, interval 16820ms.
Jun  6 10:37:47 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:37:47 lolbox dhclient: IA_NA status code NoAddrsAvail.
Jun  6 10:38:04 lolbox dhclient: XMT: Solicit on eth0, interval 34410ms.
Jun  6 10:38:04 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:38:04 lolbox dhclient: IA_NA status code NoAddrsAvail.
Jun  6 10:38:16 lolbox NetworkManager[862]: <warn> (eth0): DHCPv6 request timed out.
Jun  6 10:38:16 lolbox NetworkManager[862]: <info> (eth0): canceled DHCP transaction, DHCP client pid 13045
Jun  6 10:38:16 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 4 of 5 (IPv6 Configure Timeout) scheduled...
Jun  6 10:38:16 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 4 of 5 (IPv6 Configure Timeout) started...
Jun  6 10:38:16 lolbox NetworkManager[862]: <info> (eth0): device state change: activated -> failed (reason 'ip-config-unavailable') [100 120 5]
Jun  6 10:38:16 lolbox NetworkManager[862]: <info> NetworkManager state is now DISCONNECTED
Jun  6 10:38:16 lolbox NetworkManager[862]: <warn> Activation (eth0) failed for connection 'Wired connection 1'
Jun  6 10:38:16 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 4 of 5 (IPv6 Configure Timeout) complete.
Jun  6 10:38:16 lolbox NetworkManager[862]: <info> (eth0): device state change: failed -> disconnected (reason 'none') [120 30 0]
Jun  6 10:38:16 lolbox NetworkManager[862]: <info> (eth0): deactivating device (reason 'none') [0]
Jun  6 10:37:34 lolbox whoopsie[1133]: online
Jun  6 10:38:16 lolbox whoopsie[1133]: offline
Jun  6 10:38:16 lolbox dbus[485]: [system] Activating service name='org.freedesktop.nm_dispatcher' (using servicehelper)
Jun  6 10:38:16 lolbox dbus[485]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Jun  6 10:38:16 lolbox NetworkManager[862]: <info> (eth0): canceled DHCP transaction, DHCP client pid 13044
Jun  6 10:38:16 lolbox NetworkManager[862]: <warn> DNS: plugin dnsmasq update failed
Jun  6 10:38:16 lolbox NetworkManager[862]: <info> Removing DNS information from /sbin/resolvconf
Jun  6 10:38:16 lolbox avahi-daemon[619]: Withdrawing address record for fe80::6ef0:49ff:feb9:b17f on eth0.
Jun  6 10:38:16 lolbox avahi-daemon[619]: Leaving mDNS multicast group on interface eth0.IPv6 with address fe80::6ef0:49ff:feb9:b17f.
Jun  6 10:38:16 lolbox avahi-daemon[619]: Interface eth0.IPv6 no longer relevant for mDNS.
Jun  6 10:38:16 lolbox avahi-daemon[619]: Withdrawing address record for 192.168.0.16 on eth0.
Jun  6 10:38:16 lolbox avahi-daemon[619]: Leaving mDNS multicast group on interface eth0.IPv4 with address 192.168.0.16.
Jun  6 10:38:16 lolbox avahi-daemon[619]: Interface eth0.IPv4 no longer relevant for mDNS.
Jun  6 10:38:16 lolbox dnsmasq[1362]: setting upstream servers from DBus
Jun  6 10:38:17 lolbox avahi-daemon[619]: Joining mDNS multicast group on interface eth0.IPv6 with address fe80::6ef0:49ff:feb9:b17f.
Jun  6 10:38:17 lolbox avahi-daemon[619]: New relevant interface eth0.IPv6 for mDNS.
Jun  6 10:38:17 lolbox avahi-daemon[619]: Registering new address record for fe80::6ef0:49ff:feb9:b17f on eth0.*.
Jun  6 10:38:18 lolbox dnsmasq[1138]: no servers found in /var/run/dnsmasq/resolv.conf, will retry
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Auto-activating connection 'Wired connection 1'.
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) starting connection 'Wired connection 1'
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> (eth0): device state change: disconnected -> prepare (reason 'none') [30 40 0]
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> NetworkManager state is now CONNECTING
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) scheduled...
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) started...
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) scheduled...
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) complete.
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) starting...
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> (eth0): device state change: prepare -> config (reason 'none') [40 50 0]
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) successful.
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) scheduled.
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) complete.
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) started...
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> (eth0): device state change: config -> ip-config (reason 'none') [50 70 0]
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Beginning DHCPv4 transaction (timeout in 45 seconds)
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> dhclient started with pid 13160
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Beginning DHCPv6 transaction (timeout in 45 seconds)
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> dhclient started with pid 13161
Jun  6 10:38:18 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) complete.
Jun  6 10:38:18 lolbox avahi-daemon[619]: Withdrawing address record for fe80::6ef0:49ff:feb9:b17f on eth0.
Jun  6 10:38:18 lolbox avahi-daemon[619]: Leaving mDNS multicast group on interface eth0.IPv6 with address fe80::6ef0:49ff:feb9:b17f.
Jun  6 10:38:18 lolbox avahi-daemon[619]: Interface eth0.IPv6 no longer relevant for mDNS.
Jun  6 10:38:18 lolbox dhclient: Internet Systems Consortium DHCP Client 4.2.4
Jun  6 10:38:18 lolbox dhclient: Copyright 2004-2012 Internet Systems Consortium.
Jun  6 10:38:18 lolbox dhclient: All rights reserved.
Jun  6 10:38:18 lolbox dhclient: For info, please visit https://www.isc.org/software/dhcp/
Jun  6 10:38:18 lolbox dhclient: 
Jun  6 10:38:19 lolbox dhclient: Internet Systems Consortium DHCP Client 4.2.4
Jun  6 10:38:19 lolbox dhclient: Copyright 2004-2012 Internet Systems Consortium.
Jun  6 10:38:19 lolbox dhclient: All rights reserved.
Jun  6 10:38:19 lolbox dhclient: For info, please visit https://www.isc.org/software/dhcp/
Jun  6 10:38:19 lolbox dhclient: 
Jun  6 10:38:19 lolbox NetworkManager[862]: <info> (eth0): DHCPv4 state changed nbi -> preinit
Jun  6 10:38:19 lolbox dhclient: Bound to *:546
Jun  6 10:38:19 lolbox dhclient: Listening on Socket/eth0
Jun  6 10:38:19 lolbox dhclient: Sending on   Socket/eth0
Jun  6 10:38:19 lolbox NetworkManager[862]: <info> (eth0): DHCPv6 state changed nbi -> preinit6
Jun  6 10:38:19 lolbox dhclient: Listening on LPF/eth0/6c:f0:49:b9:b1:7f
Jun  6 10:38:19 lolbox dhclient: Sending on   LPF/eth0/6c:f0:49:b9:b1:7f
Jun  6 10:38:19 lolbox dhclient: Sending on   Socket/fallback
Jun  6 10:38:19 lolbox dhclient: DHCPREQUEST of 192.168.0.16 on eth0 to 255.255.255.255 port 67 (xid=0x3fc9376d)
Jun  6 10:38:19 lolbox dhclient: XMT: Solicit on eth0, interval 1020ms.
Jun  6 10:38:19 lolbox dhclient: send_packet6: Cannot assign requested address
Jun  6 10:38:19 lolbox dhclient: dhc6: send_packet6() sent -1 of 77 bytes
Jun  6 10:38:20 lolbox dhclient: DHCPACK of 192.168.0.16 from 192.168.0.1
Jun  6 10:38:20 lolbox dhclient: bound to 192.168.0.16 -- renewal in 41481 seconds.
Jun  6 10:38:20 lolbox NetworkManager[862]: <info> (eth0): DHCPv4 state changed preinit -> reboot
Jun  6 10:38:20 lolbox NetworkManager[862]: <info>   address 192.168.0.16
Jun  6 10:38:20 lolbox NetworkManager[862]: <info>   prefix 24 (255.255.255.0)
Jun  6 10:38:20 lolbox NetworkManager[862]: <info>   gateway 192.168.0.1
Jun  6 10:38:20 lolbox NetworkManager[862]: <info>   nameserver '83.255.245.11'
Jun  6 10:38:20 lolbox NetworkManager[862]: <info>   nameserver '193.150.193.150'
Jun  6 10:38:20 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 5 of 5 (IPv4 Configure Commit) scheduled...
Jun  6 10:38:20 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 5 of 5 (IPv4 Commit) started...
Jun  6 10:38:20 lolbox avahi-daemon[619]: Joining mDNS multicast group on interface eth0.IPv4 with address 192.168.0.16.
Jun  6 10:38:20 lolbox avahi-daemon[619]: New relevant interface eth0.IPv4 for mDNS.
Jun  6 10:38:20 lolbox avahi-daemon[619]: Registering new address record for 192.168.0.16 on eth0.IPv4.
Jun  6 10:38:20 lolbox dhclient: XMT: Solicit on eth0, interval 2110ms.
Jun  6 10:38:20 lolbox dhclient: send_packet6: Cannot assign requested address
Jun  6 10:38:20 lolbox dhclient: dhc6: send_packet6() sent -1 of 77 bytes
Jun  6 10:38:20 lolbox avahi-daemon[619]: Joining mDNS multicast group on interface eth0.IPv6 with address fe80::6ef0:49ff:feb9:b17f.
Jun  6 10:38:20 lolbox avahi-daemon[619]: New relevant interface eth0.IPv6 for mDNS.
Jun  6 10:38:20 lolbox avahi-daemon[619]: Registering new address record for fe80::6ef0:49ff:feb9:b17f on eth0.*.
Jun  6 10:38:21 lolbox NetworkManager[862]: <info> (eth0): device state change: ip-config -> secondaries (reason 'none') [70 90 0]
Jun  6 10:38:21 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 5 of 5 (IPv4 Commit) complete.
Jun  6 10:38:21 lolbox NetworkManager[862]: <info> (eth0): device state change: secondaries -> activated (reason 'none') [90 100 0]
Jun  6 10:38:21 lolbox NetworkManager[862]: <info> NetworkManager state is now CONNECTED_GLOBAL
Jun  6 10:38:21 lolbox NetworkManager[862]: <info> Policy set 'Wired connection 1' (eth0) as default for IPv4 routing and DNS.
Jun  6 10:38:21 lolbox NetworkManager[862]: <info> Writing DNS information to /sbin/resolvconf
Jun  6 10:38:21 lolbox dnsmasq[1362]: setting upstream servers from DBus
Jun  6 10:38:21 lolbox dnsmasq[1362]: using nameserver 127.0.0.1#53
Jun  6 10:38:21 lolbox dnsmasq[1362]: using nameserver 193.150.193.150#53
Jun  6 10:38:21 lolbox dnsmasq[1362]: using nameserver 83.255.245.11#53
Jun  6 10:38:21 lolbox NetworkManager[862]: <info> Activation (eth0) successful, device activated.
Jun  6 10:38:21 lolbox whoopsie[1133]: message repeated 2 times: [ offline]
Jun  6 10:38:21 lolbox whoopsie[1133]: online
Jun  6 10:38:21 lolbox ntpdate[13217]: Can't find host ntp.ubuntu.com: Name or service not known (-2)
Jun  6 10:38:21 lolbox ntpdate[13217]: no servers can be used, exiting
Jun  6 10:38:22 lolbox dnsmasq[1138]: reading /var/run/dnsmasq/resolv.conf
Jun  6 10:38:22 lolbox dnsmasq[1138]: using nameserver 127.0.1.1#53
Jun  6 10:38:22 lolbox dhclient: XMT: Solicit on eth0, interval 4080ms.
Jun  6 10:38:22 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:38:22 lolbox dhclient: IA_NA status code NoAddrsAvail.
Jun  6 10:38:26 lolbox dhclient: XMT: Solicit on eth0, interval 8450ms.
Jun  6 10:38:26 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:38:26 lolbox dhclient: IA_NA status code NoAddrsAvail.
Jun  6 10:38:35 lolbox dhclient: XMT: Solicit on eth0, interval 16630ms.
Jun  6 10:38:35 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:38:35 lolbox dhclient: IA_NA status code NoAddrsAvail.
Jun  6 10:38:51 lolbox dhclient: XMT: Solicit on eth0, interval 34860ms.
Jun  6 10:38:51 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:38:51 lolbox dhclient: IA_NA status code NoAddrsAvail.
Jun  6 10:38:58 lolbox dnsmasq[1138]: Maximum number of concurrent DNS queries reached (max: 150)
Jun  6 10:38:58 lolbox dnsmasq[1362]: Maximum number of concurrent DNS queries reached (max: 150)
Jun  6 10:39:04 lolbox NetworkManager[862]: <warn> (eth0): DHCPv6 request timed out.
Jun  6 10:39:04 lolbox NetworkManager[862]: <info> (eth0): canceled DHCP transaction, DHCP client pid 13161
Jun  6 10:39:04 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 4 of 5 (IPv6 Configure Timeout) scheduled...
Jun  6 10:39:04 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 4 of 5 (IPv6 Configure Timeout) started...
Jun  6 10:39:04 lolbox NetworkManager[862]: <info> (eth0): device state change: activated -> failed (reason 'ip-config-unavailable') [100 120 5]
Jun  6 10:39:04 lolbox NetworkManager[862]: <info> NetworkManager state is now DISCONNECTED
Jun  6 10:39:04 lolbox NetworkManager[862]: <warn> Activation (eth0) failed for connection 'Wired connection 1'
Jun  6 10:38:22 lolbox whoopsie[1133]: online
Jun  6 10:39:04 lolbox whoopsie[1133]: offline
Jun  6 10:39:04 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 4 of 5 (IPv6 Configure Timeout) complete.
Jun  6 10:39:04 lolbox dbus[485]: [system] Activating service name='org.freedesktop.nm_dispatcher' (using servicehelper)
Jun  6 10:39:04 lolbox NetworkManager[862]: <info> (eth0): device state change: failed -> disconnected (reason 'none') [120 30 0]
Jun  6 10:39:04 lolbox NetworkManager[862]: <info> (eth0): deactivating device (reason 'none') [0]
Jun  6 10:39:04 lolbox dbus[485]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
Jun  6 10:39:04 lolbox NetworkManager[862]: <info> (eth0): canceled DHCP transaction, DHCP client pid 13160
Jun  6 10:39:04 lolbox avahi-daemon[619]: Withdrawing address record for fe80::6ef0:49ff:feb9:b17f on eth0.
Jun  6 10:39:04 lolbox avahi-daemon[619]: Leaving mDNS multicast group on interface eth0.IPv6 with address fe80::6ef0:49ff:feb9:b17f.
Jun  6 10:39:04 lolbox avahi-daemon[619]: Interface eth0.IPv6 no longer relevant for mDNS.
Jun  6 10:39:04 lolbox avahi-daemon[619]: Withdrawing address record for 192.168.0.16 on eth0.
Jun  6 10:39:04 lolbox avahi-daemon[619]: Leaving mDNS multicast group on interface eth0.IPv4 with address 192.168.0.16.
Jun  6 10:39:04 lolbox avahi-daemon[619]: Interface eth0.IPv4 no longer relevant for mDNS.
Jun  6 10:39:04 lolbox NetworkManager[862]: <warn> DNS: plugin dnsmasq update failed
Jun  6 10:39:04 lolbox NetworkManager[862]: <info> Removing DNS information from /sbin/resolvconf
Jun  6 10:39:04 lolbox dnsmasq[1362]: setting upstream servers from DBus
Jun  6 10:39:05 lolbox avahi-daemon[619]: Joining mDNS multicast group on interface eth0.IPv6 with address fe80::6ef0:49ff:feb9:b17f.
Jun  6 10:39:05 lolbox avahi-daemon[619]: New relevant interface eth0.IPv6 for mDNS.
Jun  6 10:39:05 lolbox avahi-daemon[619]: Registering new address record for fe80::6ef0:49ff:feb9:b17f on eth0.*.
Jun  6 10:39:06 lolbox dnsmasq[1138]: no servers found in /var/run/dnsmasq/resolv.conf, will retry
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Auto-activating connection 'Wired connection 1'.
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) starting connection 'Wired connection 1'
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> (eth0): device state change: disconnected -> prepare (reason 'none') [30 40 0]
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> NetworkManager state is now CONNECTING
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) scheduled...
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) started...
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) scheduled...
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) complete.
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) starting...
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> (eth0): device state change: prepare -> config (reason 'none') [40 50 0]
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) successful.
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) scheduled.
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) complete.
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) started...
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> (eth0): device state change: config -> ip-config (reason 'none') [50 70 0]
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Beginning DHCPv4 transaction (timeout in 45 seconds)
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> dhclient started with pid 13270
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Beginning DHCPv6 transaction (timeout in 45 seconds)
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> dhclient started with pid 13271
Jun  6 10:39:07 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) complete.
Jun  6 10:39:07 lolbox avahi-daemon[619]: Withdrawing address record for fe80::6ef0:49ff:feb9:b17f on eth0.
Jun  6 10:39:07 lolbox avahi-daemon[619]: Leaving mDNS multicast group on interface eth0.IPv6 with address fe80::6ef0:49ff:feb9:b17f.
Jun  6 10:39:07 lolbox avahi-daemon[619]: Interface eth0.IPv6 no longer relevant for mDNS.
Jun  6 10:39:07 lolbox dhclient: Internet Systems Consortium DHCP Client 4.2.4
Jun  6 10:39:07 lolbox dhclient: Copyright 2004-2012 Internet Systems Consortium.
Jun  6 10:39:07 lolbox dhclient: All rights reserved.
Jun  6 10:39:07 lolbox dhclient: For info, please visit https://www.isc.org/software/dhcp/
Jun  6 10:39:07 lolbox dhclient: 
Jun  6 10:39:08 lolbox dhclient: Internet Systems Consortium DHCP Client 4.2.4
Jun  6 10:39:08 lolbox dhclient: Copyright 2004-2012 Internet Systems Consortium.
Jun  6 10:39:08 lolbox dhclient: All rights reserved.
Jun  6 10:39:08 lolbox dhclient: For info, please visit https://www.isc.org/software/dhcp/
Jun  6 10:39:08 lolbox dhclient: 
Jun  6 10:39:08 lolbox dhclient: Bound to *:546
Jun  6 10:39:08 lolbox dhclient: Listening on Socket/eth0
Jun  6 10:39:08 lolbox dhclient: Sending on   Socket/eth0
Jun  6 10:39:08 lolbox kernel: [ 1446.098590] type=1400 audit(1402043948.002:75): apparmor="DENIED" operation="signal" profile="/usr/lib/NetworkManager/nm-dhcp-client.action" pid=13273 comm="nm-dhcp-client." requested_mask="send" denied_mask="send" signal=term peer="/sbin/dhclient"
Jun  6 10:39:08 lolbox kernel: [ 1446.098599] type=1400 audit(1402043948.002:76): apparmor="DENIED" operation="signal" profile="/sbin/dhclient" pid=13273 comm="nm-dhcp-client." requested_mask="receive" denied_mask="receive" signal=term peer="/usr/lib/NetworkManager/nm-dhcp-client.action"
Jun  6 10:39:08 lolbox NetworkManager[862]: <info> (eth0): DHCPv4 state changed nbi -> preinit
Jun  6 10:39:08 lolbox dhclient: Listening on LPF/eth0/6c:f0:49:b9:b1:7f
Jun  6 10:39:08 lolbox dhclient: Sending on   LPF/eth0/6c:f0:49:b9:b1:7f
Jun  6 10:39:08 lolbox dhclient: Sending on   Socket/fallback
Jun  6 10:39:08 lolbox dhclient: DHCPREQUEST of 192.168.0.16 on eth0 to 255.255.255.255 port 67 (xid=0x3e0183b9)
Jun  6 10:39:08 lolbox dhclient: XMT: Solicit on eth0, interval 1050ms.
Jun  6 10:39:08 lolbox dhclient: send_packet6: Cannot assign requested address
Jun  6 10:39:08 lolbox dhclient: dhc6: send_packet6() sent -1 of 77 bytes
Jun  6 10:39:09 lolbox dhclient: DHCPACK of 192.168.0.16 from 192.168.0.1
Jun  6 10:39:09 lolbox dhclient: bound to 192.168.0.16 -- renewal in 35498 seconds.
Jun  6 10:39:09 lolbox NetworkManager[862]: <info> (eth0): DHCPv4 state changed preinit -> reboot
Jun  6 10:39:09 lolbox NetworkManager[862]: <info>   address 192.168.0.16
Jun  6 10:39:09 lolbox NetworkManager[862]: <info>   prefix 24 (255.255.255.0)
Jun  6 10:39:09 lolbox NetworkManager[862]: <info>   gateway 192.168.0.1
Jun  6 10:39:09 lolbox NetworkManager[862]: <info>   nameserver '83.255.245.11'
Jun  6 10:39:09 lolbox NetworkManager[862]: <info>   nameserver '193.150.193.150'
Jun  6 10:39:09 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 5 of 5 (IPv4 Configure Commit) scheduled...
Jun  6 10:39:09 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 5 of 5 (IPv4 Commit) started...
Jun  6 10:39:09 lolbox avahi-daemon[619]: Joining mDNS multicast group on interface eth0.IPv4 with address 192.168.0.16.
Jun  6 10:39:09 lolbox avahi-daemon[619]: New relevant interface eth0.IPv4 for mDNS.
Jun  6 10:39:09 lolbox avahi-daemon[619]: Registering new address record for 192.168.0.16 on eth0.IPv4.
Jun  6 10:39:09 lolbox avahi-daemon[619]: Joining mDNS multicast group on interface eth0.IPv6 with address fe80::6ef0:49ff:feb9:b17f.
Jun  6 10:39:09 lolbox avahi-daemon[619]: New relevant interface eth0.IPv6 for mDNS.
Jun  6 10:39:09 lolbox avahi-daemon[619]: Registering new address record for fe80::6ef0:49ff:feb9:b17f on eth0.*.
Jun  6 10:39:10 lolbox dhclient: XMT: Solicit on eth0, interval 2180ms.
Jun  6 10:39:10 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:39:10 lolbox dhclient: IA_NA status code NoAddrsAvail.
Jun  6 10:39:10 lolbox NetworkManager[862]: <info> (eth0): device state change: ip-config -> secondaries (reason 'none') [70 90 0]
Jun  6 10:39:10 lolbox NetworkManager[862]: <info> Activation (eth0) Stage 5 of 5 (IPv4 Commit) complete.
Jun  6 10:39:10 lolbox NetworkManager[862]: <info> (eth0): device state change: secondaries -> activated (reason 'none') [90 100 0]
Jun  6 10:39:10 lolbox NetworkManager[862]: <info> NetworkManager state is now CONNECTED_GLOBAL
Jun  6 10:39:10 lolbox NetworkManager[862]: <info> Policy set 'Wired connection 1' (eth0) as default for IPv4 routing and DNS.
Jun  6 10:39:10 lolbox NetworkManager[862]: <info> Writing DNS information to /sbin/resolvconf
Jun  6 10:39:10 lolbox dnsmasq[1362]: setting upstream servers from DBus
Jun  6 10:39:10 lolbox dnsmasq[1362]: using nameserver 127.0.0.1#53
Jun  6 10:39:10 lolbox dnsmasq[1362]: using nameserver 193.150.193.150#53
Jun  6 10:39:10 lolbox dnsmasq[1362]: using nameserver 83.255.245.11#53
Jun  6 10:39:10 lolbox NetworkManager[862]: <info> Activation (eth0) successful, device activated.
Jun  6 10:39:10 lolbox whoopsie[1133]: message repeated 2 times: [ offline]
Jun  6 10:39:10 lolbox whoopsie[1133]: online
Jun  6 10:39:10 lolbox ntpdate[13339]: Can't find host ntp.ubuntu.com: Name or service not known (-2)
Jun  6 10:39:10 lolbox ntpdate[13339]: no servers can be used, exiting
Jun  6 10:39:11 lolbox dnsmasq[1138]: reading /var/run/dnsmasq/resolv.conf
Jun  6 10:39:11 lolbox dnsmasq[1138]: using nameserver 127.0.1.1#53
Jun  6 10:39:12 lolbox dhclient: XMT: Solicit on eth0, interval 4350ms.
Jun  6 10:39:12 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:39:12 lolbox dhclient: IA_NA status code NoAddrsAvail.
Jun  6 10:39:16 lolbox dhclient: XMT: Solicit on eth0, interval 8740ms.
Jun  6 10:39:16 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:39:16 lolbox dhclient: IA_NA status code NoAddrsAvail.
Jun  6 10:39:17 lolbox dnsmasq[1138]: Maximum number of concurrent DNS queries reached (max: 150)
Jun  6 10:39:17 lolbox dnsmasq[1362]: Maximum number of concurrent DNS queries reached (max: 150)
Jun  6 10:39:25 lolbox dhclient: XMT: Solicit on eth0, interval 17610ms.
Jun  6 10:39:25 lolbox dhclient: RCV: Advertise message on eth0 from fe80::120d:7fff:fe97:9d54.
Jun  6 10:39:25 lolbox dhclient: IA_NA status code NoAddrsAvail.

/etc/NetworkManager/NetworkManager.conf:

[main]
plugins=ifupdown,keyfile,ofono
dns=dnsmasq

#no-auto-default=6C:F0:49:B9:B1:7F,

[ifupdown]
managed=false

/etc/network/interfaces:

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback

lshw -C network:

  ➜  ~  sudo lshw -C network
    *-network               
         description: Ethernet interface
         product: RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller
         vendor: Realtek Semiconductor Co., Ltd.
         physical id: 0
         bus info: pci@0000:04:00.0
         logical name: eth0
         version: 03
         serial: 6c:f0:49:b9:b1:7f
         size: 1Gbit/s
         capacity: 1Gbit/s
         width: 64 bits
         clock: 33MHz
         capabilities: pm msi pciexpress msix vpd bus_master cap_list rom ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
         configuration: autonegotiation=on broadcast=yes driver=r8168 driverversion=8.038.00-NAPI duplex=full latency=0 link=yes multicast=yes port=twisted pair speed=1Gbit/s
         resources: irq:48 ioport:de00(size=256) memory:fbeff000-fbefffff memory:fbef8000-fbefbfff memory:fbe00000-fbe1ffff
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2 Answers 2

up vote 0 down vote accepted

I'm not entirely sure why this worked, but it seems to have. It's not an ideal solution, but at least it works.

What I did was that I removed the address reservation I had set in my router, and set IPv4 Settings → Method to "Automatic (DHCP)" instead of "Manual" (I had previously tried to set it manually, which "worked", but didn't resolve my issue). I also set IPv6 Settings → Method to "Ignore" just on a hunch.

After that, I restarted the resolveconf and network-manager services, but it didn't seem to help. So I tried restarting the networking service, which failed. After googling a bit, it seems that's not a supported way of restarting your network interfaces, so I restarted them manually instead:

sudo ifdown --exclude=lo -a && sudo ifup --exclude=lo -a

That seems to have done the trick. I'm not sure if the static IP assignment had anything to do with it, or if it was disabling IPv6, but either way, it works now.

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I had this same intermittent network connectivity problem after upgrading to kubuntu 14.04 from 12.x On a hunch I searched for a "switching off ipv6" page and found askubuntu: disabling ipv6. I followed those sysctl steps and now the problem seems solved. Bargain.

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