The failure had not recurred until today. My slightly amended version of the script provided above by Steve Chadsey (schadsey), 2017-07-19, https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1586528/comments/18 did not rectify the problem. I have since modified it more and hope that it can provide useful diagnostics next time there is a similar failure.
The connection was active until after 00:49:01. It was restored manually by 08:11:59. Unfortunately, I cannot be certain whether I reactivated the interface or whether an automated script did so.
Notice that the counts of packets and bytes had been increasing, and that no packets had been dropped.
yoyo ~ # ip a add 192.168.42.187 dev eth0
yoyo ~ # ip a s eth0
2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN group
default qlen 1000
link/ether 00:25:64:72:72:14 brd ff:ff:ff:ff:ff:ff
inet 192.168.42.187/32 scope global eth0
valid_lft forever preferred_lft forever
yoyo ~ # ip a del 192.168.42.187 dev eth0
Warning: Executing wildcard deletion to stay compatible with old scripts.
Explicitly specify the prefix length (192.168.42.187/32) to avoid
this warning.
This special behaviour is likely to disappear in further releases,
fix your scripts!
yoyo ~ # ip a s eth0
2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN group
default qlen 1000
link/ether 00:25:64:72:72:14 brd ff:ff:ff:ff:ff:ff
yoyo ~ # ip a add 192.168.42.187/24 dev eth0
yoyo ~ # ip a s eth0
2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN group
default qlen 1000
link/ether 00:25:64:72:72:14 brd ff:ff:ff:ff:ff:ff
inet 192.168.42.187/24 scope global eth0
valid_lft forever preferred_lft forever
One surprising discovery was that a virtual machine maintained its connection through the same interface that the physical host had lost. Also, the network manager icon was missing from the task bar (though it may have gone because of my actions).
On the physical host, the D.H.C.P. daemon "dhclient" had terminated. Its last known activity was at 01:18:47.
[LinuxMint] graham@yoyo $ grep "dhclient" /var/log/daemon.log | tail -n 4
Sep 1 01:17:08 yoyo dhclient[20006]: DHCPREQUEST of 192.168.42.187 on eth0 to 255.255.255.255 port 67 (xid=0x458de0a7)
Sep 1 01:18:02 yoyo dhclient[20006]: message repeated 4 times: [ DHCPREQUEST of 192.168.42.187 on eth0 to 255.255.255.255 port 67 (xid=0x458de0a7)]
Sep 1 01:18:23 yoyo dhclient[20006]: DHCPREQUEST of 192.168.42.187 on eth0 to 255.255.255.255 port 67 (xid=0x458de0a7)
Sep 1 01:18:47 yoyo dhclient[20006]: message repeated 2 times: [ DHCPREQUEST of 192.168.42.187 on eth0 to 255.255.255.255 port 67 (xid=0x458de0a7)]
Fri Sep 01 12:33:22 ~
Here is an except from /var/log/daemon.log showing activities of avahi-daemon:
Sep 1 00:48:54 yoyo dhclient[20006]: DHCPACK of 192.168.42.187 from 192.168.42.129
Sep 1 00:48:54 yoyo dhclient[20006]: bound to 192.168.42.187 -- renewal in 708 seconds.
Sep 1 00:53:07 yoyo avahi-daemon[1017]: Withdrawing address record for 192.168.42.187 on eth0.
Sep 1 00:53:07 yoyo avahi-daemon[1017]: Leaving mDNS multicast group on interface eth0.IPv4 with address 192.168.42.187.
Sep 1 00:53:07 yoyo avahi-daemon[1017]: Interface eth0.IPv4 no longer relevant for mDNS.
Sep 1 00:53:09 yoyo ntpd[20331]: Deleting interface #3 eth0, 192.168.42.187#123, interface stats: received=11901, sent=12617, dropped=0, active_time=611380 secs
Sep 1 00:53:09 yoyo ntpd[20331]: 85.199.214.102 local addr 192.168.42.187 -> <null>
...
Sep 1 08:11:36 yoyo ntpd[2507]: error resolving pool 0.ubuntu.pool.ntp.org: Temporary failure in name resolution (-3)
Sep 1 08:11:59 yoyo avahi-daemon[1017]: Joining mDNS multicast group on interface eth0.IPv4 with address 192.168.42.187.
Sep 1 08:11:59 yoyo avahi-daemon[1017]: New relevant interface eth0.IPv4 for mDNS.
Sep 1 08:11:59 yoyo avahi-daemon[1017]: Registering new address record for 192.168.42.187 on eth0.IPv4.
Sep 1 08:12:02 yoyo systemd[1]: Started Network Manager.
The failure had not recurred until today. My slightly amended version of the script provided above by Steve Chadsey (schadsey), 2017-07-19, https:/ /bugs.launchpad .net/ubuntu/ +source/ avahi/+ bug/1586528/ comments/ 18 did not rectify the problem. I have since modified it more and hope that it can provide useful diagnostics next time there is a similar failure.
The connection was active until after 00:49:01. It was restored manually by 08:11:59. Unfortunately, I cannot be certain whether I reactivated the interface or whether an automated script did so.
yoyo ~ # ifconfig eth0 4b25:5c64: f669/64 Scope:Link
collisions: 0 txqueuelen:1000
Interrupt: 18
eth0 Link encap:Ethernet HWaddr 00:25:64:72:72:14
inet6 addr: fe80::c1e6:
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:65340342 errors:0 dropped:0 overruns:0 frame:0
TX packets:26833432 errors:0 dropped:0 overruns:0 carrier:0
RX bytes:21650436815 (21.6 GB) TX bytes:140523812727 (140.5 GB)
yoyo ~ # ifconfig eth0 down ------- ------- ^^^^^^^ ^------ ------- -----^ ------- ------- ^^^^^^^ ^------ ------- -----^
collisions: 0 txqueuelen:1000 ------- -----^^ ^^^^^^^ ^^----- ------- ------- --^^^^^ ^^^^^^^
Interrupt: 18
yoyo ~ # ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:25:64:72:72:14
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:65340378 errors:0 dropped:0 overruns:0 frame:0
-------
TX packets:26833625 errors:0 dropped:0 overruns:0 carrier:0
-------
RX bytes:21650441164 (21.6 GB) TX bytes:140523828704 (140.5 GB)
-------
Notice that the counts of packets and bytes had been increasing, and that no packets had been dropped.
yoyo ~ # ip a add 192.168.42.187 dev eth0
yoyo ~ # ip a s eth0 MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN group
2: eth0: <BROADCAST,
default qlen 1000
link/ether 00:25:64:72:72:14 brd ff:ff:ff:ff:ff:ff
inet 192.168.42.187/32 scope global eth0
valid_lft forever preferred_lft forever
yoyo ~ # ip a del 192.168.42.187 dev eth0
Warning: Executing wildcard deletion to stay compatible with old scripts.
Explicitly specify the prefix length (192.168.42.187/32) to avoid
this warning.
This special behaviour is likely to disappear in further releases,
fix your scripts!
yoyo ~ # ip a s eth0 MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN group
2: eth0: <BROADCAST,
default qlen 1000
link/ether 00:25:64:72:72:14 brd ff:ff:ff:ff:ff:ff
yoyo ~ # ip a add 192.168.42.187/24 dev eth0
yoyo ~ # ip a s eth0 MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN group
2: eth0: <BROADCAST,
default qlen 1000
link/ether 00:25:64:72:72:14 brd ff:ff:ff:ff:ff:ff
inet 192.168.42.187/24 scope global eth0
valid_lft forever preferred_lft forever
yoyo ~ # ifconfig eth0 255.255. 0yoyo ~ # ifconfig eth0 ------- ------- ------- ------- ------- -----^^ ^
collisions: 0 txqueuelen:1000
Interrupt: 18
eth0 Link encap:Ethernet HWaddr 00:25:64:72:72:14
inet addr:192.168.42.187 Bcast:0.0.0.0 Mask:255.
eth0 Link encap:Ethernet HWaddr 00:25:64:72:72:14
inet addr:192.168.42.187 Bcast:0.0.0.0 Mask:255.255.255.0
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:65340544 errors:0 dropped:357 overruns:0 frame:0
-------
TX packets:26834217 errors:0 dropped:0 overruns:0 carrier:0
RX bytes:21650460079 (21.6 GB) TX bytes:140523878283 (140.5 GB)
Now there are dropped packets.
yoyo ~ # ifconfig eth0 ------- ------- ------- ------- ------- -----^^ ^
collisions: 0 txqueuelen:1000
Interrupt: 18
eth0 Link encap:Ethernet HWaddr 00:25:64:72:72:14
inet addr:192.168.42.187 Bcast:0.0.0.0 Mask:255.255.255.0
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:65340544 errors:0 dropped:638 overruns:0 frame:0
-------
TX packets:26834217 errors:0 dropped:0 overruns:0 carrier:0
RX bytes:21650460079 (21.6 GB) TX bytes:140523878283 (140.5 GB)
More packets have been dropped.
yoyo ~ # ifconfig eth0 down
collisions: 0 txqueuelen:1000
Interrupt: 18
yoyo ~ # ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:25:64:72:72:14
inet addr:192.168.42.187 Bcast:0.0.0.0 Mask:255.255.255.0
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:65340544 errors:0 dropped:687 overruns:0 frame:0
TX packets:26834217 errors:0 dropped:0 overruns:0 carrier:0
RX bytes:21650460079 (21.6 GB) TX bytes:140523878283 (140.5 GB)
Oops. My memory let me down:-
yoyo ~ # ifconfig eth0 up dhcp 64ff:fe72: 7214/64 Scope:Link
collisions: 0 txqueuelen:1000
Interrupt: 18
dhcp: Unknown host
ifconfig: `--help' gives usage information.
yoyo ~ # ifconfig eth0
eth0 Link encap:Ethernet HWaddr 00:25:64:72:72:14
inet addr:192.168.42.187 Bcast:0.0.0.0 Mask:255.255.255.0
inet6 addr: fe80::225:
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
!---------^^
RX packets:65340857 errors:0 dropped:697 overruns:0 frame:0
TX packets:26834733 errors:0 dropped:0 overruns:0 carrier:0
RX bytes:21650604853 (21.6 GB) TX bytes:140523968671 (140.5 GB)
One surprising discovery was that a virtual machine maintained its connection through the same interface that the physical host had lost. Also, the network manager icon was missing from the task bar (though it may have gone because of my actions).
On the physical host, the D.H.C.P. daemon "dhclient" had terminated. Its last known activity was at 01:18:47.
[LinuxMint] graham@yoyo $ grep "dhclient" /var/log/daemon.log | tail -n 4
Sep 1 01:17:08 yoyo dhclient[20006]: DHCPREQUEST of 192.168.42.187 on eth0 to 255.255.255.255 port 67 (xid=0x458de0a7)
Sep 1 01:18:02 yoyo dhclient[20006]: message repeated 4 times: [ DHCPREQUEST of 192.168.42.187 on eth0 to 255.255.255.255 port 67 (xid=0x458de0a7)]
Sep 1 01:18:23 yoyo dhclient[20006]: DHCPREQUEST of 192.168.42.187 on eth0 to 255.255.255.255 port 67 (xid=0x458de0a7)
Sep 1 01:18:47 yoyo dhclient[20006]: message repeated 2 times: [ DHCPREQUEST of 192.168.42.187 on eth0 to 255.255.255.255 port 67 (xid=0x458de0a7)]
Fri Sep 01 12:33:22 ~
Here is an except from /var/log/daemon.log showing activities of avahi-daemon: pool.ntp. org: Temporary failure in name resolution (-3)
Sep 1 00:48:54 yoyo dhclient[20006]: DHCPACK of 192.168.42.187 from 192.168.42.129
Sep 1 00:48:54 yoyo dhclient[20006]: bound to 192.168.42.187 -- renewal in 708 seconds.
Sep 1 00:53:07 yoyo avahi-daemon[1017]: Withdrawing address record for 192.168.42.187 on eth0.
Sep 1 00:53:07 yoyo avahi-daemon[1017]: Leaving mDNS multicast group on interface eth0.IPv4 with address 192.168.42.187.
Sep 1 00:53:07 yoyo avahi-daemon[1017]: Interface eth0.IPv4 no longer relevant for mDNS.
Sep 1 00:53:09 yoyo ntpd[20331]: Deleting interface #3 eth0, 192.168.42.187#123, interface stats: received=11901, sent=12617, dropped=0, active_time=611380 secs
Sep 1 00:53:09 yoyo ntpd[20331]: 85.199.214.102 local addr 192.168.42.187 -> <null>
...
Sep 1 08:11:36 yoyo ntpd[2507]: error resolving pool 0.ubuntu.
Sep 1 08:11:59 yoyo avahi-daemon[1017]: Joining mDNS multicast group on interface eth0.IPv4 with address 192.168.42.187.
Sep 1 08:11:59 yoyo avahi-daemon[1017]: New relevant interface eth0.IPv4 for mDNS.
Sep 1 08:11:59 yoyo avahi-daemon[1017]: Registering new address record for 192.168.42.187 on eth0.IPv4.
Sep 1 08:12:02 yoyo systemd[1]: Started Network Manager.