[--- start of script output excerpts ---] 2017-09-27T13:54:08+0100 /etc/init.d/network-manager status =========================================================== ... Sep 27 13:48:38 yoyo dhclient[6050]: DHCPREQUEST of 192.168.42.187 on eth0 to 192.168.42.129 port 67 (xid=0x5160242b) Sep 27 13:48:38 yoyo dhclient[6050]: DHCPACK of 192.168.42.187 from 192.168.42.129 Sep 27 13:48:38 yoyo dhclient[6050]: bound to 192.168.42.187 -- renewal in 699 seconds. ---------------- 2017-09-27T13:54:13+0100 lsmod | grep wl ======================================== wl 6447104 0 cfg80211 565248 3 wl,mac80211,rt2x00lib ---------------- 2017-09-27T13:54:13+0100 ifconfig eth0 ====================================== eth0 Link encap:Ethernet HWaddr 00:25:64:72:72:14 inet6 addr: fe80::c1e6:4b25:5c64:f669/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:7386005 errors:0 dropped:0 overruns:0 frame:0 TX packets:2596170 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2441363610 (2.4 GB) TX bytes:18697405825 (18.6 GB) Interrupt:18 ---------------- 2017-09-27T13:54:13+0100 ip address show eth0 ============================================= 2: eth0: mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 00:25:64:72:72:14 brd ff:ff:ff:ff:ff:ff inet6 fe80::c1e6:4b25:5c64:f669/64 scope link valid_lft forever preferred_lft forever ---------------- 2017-09-27T13:54:13+0100 ls -lA /var/run/dhclient* ================================================== -rw-r--r-- 1 root root 5 Sep 27 13:48 /var/run/dhclient-eth0.pid ---------------- 2017-09-27T13:54:13+0100 ps aux | grep -v grep | grep dhc ========================================================= root 6050 0.0 0.0 16132 1024 ? S Sep25 0:00 /sbin/dhclient -d -q -sf /usr/lib/NetworkManager/nm-dhcp-helper -pf /var/run/dhclient-eth0.pid -lf /var/lib/NetworkManager/dhclient-3339a4b3-ef0a-3db1-acf1-9b810d040dfe-eth0.lease -cf /var/lib/NetworkManager/dhclient-eth0.conf eth0 ---------------- 2017-09-27T13:54:13+0100 iptables -n -v -L ========================================== Chain INPUT (policy ACCEPT 6873K packets, 2076M bytes) pkts bytes target prot opt in out source destination Chain FORWARD (policy ACCEPT 0 packets, 0 bytes) pkts bytes target prot opt in out source destination Chain OUTPUT (policy ACCEPT 2352K packets, 18G bytes) pkts bytes target prot opt in out source destination ---------------- 2017-09-27T13:54:14+0100 service network-manager restart ======================================================== Job for NetworkManager.service failed because a timeout was exceeded. See "systemctl status NetworkManager.service" and "journalctl -xe" for details. ---------------- 2017-09-27T13:56:06+0100 service networking restart =================================================== ---------------- 2017-09-27T13:56:28+0100 ifconfig eth0 down =========================================== ---------------- 2017-09-27T13:56:28+0100 ifconfig eth0 up ========================================= ---------------- [--- end of script output excerpts ---] [LinuxMint] graham@yoyo $ ip neigh show 192.168.42.248 dev eth0 lladdr 00:1b:b9:be:95:46 STALE 192.168.42.129 dev eth0 lladdr 00:50:04:23:f7:80 STALE Wed Sep 27 13:57:14 /mnt/share/work/2017-07-15_WAH [LinuxMint] graham@yoyo $ ip route Wed Sep 27 13:57:19 /mnt/share/work/2017-07-15_WAH [LinuxMint] graham@yoyo $ route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface Wed Sep 27 13:57:24 /mnt/share/work/2017-07-15_WAH [LinuxMint] graham@yoyo $ ip a s 1: lo: mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 00:25:64:72:72:14 brd ff:ff:ff:ff:ff:ff 3: wlan0: mtu 1500 qdisc noop state DOWN group default qlen 1000 link/ether 70:1a:04:89:1d:18 brd ff:ff:ff:ff:ff:ff 4: wlx9444528649bd: mtu 1500 qdisc noop state DOWN group default qlen 1000 link/ether 94:44:52:86:49:bd brd ff:ff:ff:ff:ff:ff Wed Sep 27 13:57:29 /mnt/share/work/2017-07-15_WAH [=== I got the syntax wrong next ===] [LinuxMint] graham@yoyo $ ifc=wlx9444528649bd sudo ifconfig -v ${ifc} down ; sleep 3 ; sudo ifconfig -v ${ifc} up ; sleep 2 ; sudo /sbin/dhclient -v ${ifc} ; ifconfig ${ifc} down: error fetching interface information: Device not found up: error fetching interface information: Device not found Internet Systems Consortium DHCP Client 4.3.3 Copyright 2004-2015 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ RTNETLINK answers: Operation not possible due to RF-kill RTNETLINK answers: Operation not possible due to RF-kill Listening on LPF/wlx9444528649bd/94:44:52:86:49:bd Sending on LPF/wlx9444528649bd/94:44:52:86:49:bd Listening on LPF/wlan0/70:1a:04:89:1d:18 Sending on LPF/wlan0/70:1a:04:89:1d:18 Listening on LPF/eth0/00:25:64:72:72:14 Sending on LPF/eth0/00:25:64:72:72:14 Sending on Socket/fallback DHCPDISCOVER on wlx9444528649bd to 255.255.255.255 port 67 interval 3 (xid=0x196e1439) send_packet: Network is down dhclient.c:2098: Failed to send 300 byte long packet over wlx9444528649bd interface. DHCPDISCOVER on wlan0 to 255.255.255.255 port 67 interval 3 (xid=0x9772b314) send_packet: Network is down dhclient.c:2098: Failed to send 300 byte long packet over wlan0 interface. DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 3 (xid=0x43e88f24) receive_packet failed on wlx9444528649bd: Network is down receive_packet failed on wlan0: Network is down DHCPREQUEST of 192.168.42.224 on eth0 to 255.255.255.255 port 67 (xid=0x248fe843) DHCPOFFER of 192.168.42.224 from 192.168.42.129 DHCPACK of 192.168.42.224 from 192.168.42.129 bound to 192.168.42.224 -- renewal in 736 seconds. eth0 Link encap:Ethernet HWaddr 00:25:64:72:72:14 inet addr:192.168.42.224 Bcast:192.168.42.255 Mask:255.255.255.128 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:7387015 errors:0 dropped:0 overruns:0 frame:0 TX packets:2598037 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2441536173 (2.4 GB) TX bytes:18697624650 (18.6 GB) Interrupt:18 ... [--- I wondered what would happen if the "eth0" connection bounced ---] [LinuxMint] graham@yoyo $ ifc=eth0 ; export ifc ; sudo ifconfig -v ${ifc} down ; sleep 3 ; sudo ifconfig -v ${ifc} up ; sleep 2 ; sudo /sbin/dhclient -v ${ifc} ; ifconfig ${ifc} Internet Systems Consortium DHCP Client 4.3.3 Copyright 2004-2015 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ Corrupt lease file - possible data loss! [^^^^^^^^^^^^^^^^^] Listening on LPF/eth0/00:25:64:72:72:14 Sending on LPF/eth0/00:25:64:72:72:14 Sending on Socket/fallback DHCPREQUEST of 192.168.42.224 on eth0 to 255.255.255.255 port 67 (xid=0x66aff481) DHCPACK of 192.168.42.224 from 192.168.42.129 bound to 192.168.42.224 -- renewal in 787 seconds. eth0 Link encap:Ethernet HWaddr 00:25:64:72:72:14 inet addr:192.168.42.224 Bcast:192.168.42.255 Mask:255.255.255.128 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:7418126 errors:0 dropped:0 overruns:0 frame:0 TX packets:2619530 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:2477016776 (2.4 GB) TX bytes:18700181729 (18.7 GB) Interrupt:18 [--- ifconfig shows only one address ---] ... [LinuxMint] graham@yoyo $ systemctl status NetworkManager ● NetworkManager.service - Network Manager Loaded: loaded (/lib/systemd/system/NetworkManager.service; enabled; vendor p Active: active (running) since Wed 2017-09-27 14:07:22 BST; 20min ago Docs: man:NetworkManager(8) Main PID: 23615 (NetworkManager) CGroup: /system.slice/NetworkManager.service ├─23615 /usr/sbin/NetworkManager --no-daemon ├─25324 /sbin/dhclient -d -q -sf /usr/lib/NetworkManager/nm-dhcp-help └─25359 /usr/sbin/dnsmasq --no-resolv --keep-in-foreground --no-hosts Sep 27 14:28:01 yoyo NetworkManager[23615]: [1506518881.8316] device (et Sep 27 14:28:01 yoyo dhclient[25324]: bound to 192.168.42.187 -- renewal in 782 Sep 27 14:28:02 yoyo dnsmasq[25359]: started, version 2.75 cache disabled Sep 27 14:28:02 yoyo dnsmasq[25359]: compile time options: IPv6 GNU-getopt DBus Sep 27 14:28:02 yoyo NetworkManager[23615]: [1506518882.1270] dnsmasq[0x Sep 27 14:28:02 yoyo dnsmasq[25359]: DBus support enabled: connected to system b Sep 27 14:28:02 yo[LinuxMint] graham@yoyo $ ip a s 1: lo: mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 00:25:64:72:72:14 brd ff:ff:ff:ff:ff:ff inet 192.168.42.224/25 brd 192.168.42.255 scope global eth0 valid_lft forever preferred_lft forever inet 192.168.42.187/25 brd 192.168.42.255 scope global secondary dynamic eth0 [--- note that there are two I.P. addresses associated with one interface ---] valid_lft 1760sec preferred_lft 1760sec inet6 fe80::c1e6:4b25:5c64:f669/64 scope link valid_lft forever preferred_lft forever 3: wlan0: mtu 1500 qdisc noop state DOWN group default qlen 1000 link/ether 70:1a:04:89:1d:18 brd ff:ff:ff:ff:ff:ff 4: wlx9444528649bd: mtu 1500 qdisc noop state DOWN group default qlen 1000 link/ether 94:44:52:86:49:bd brd ff:ff:ff:ff:ff:ff Wed Sep 27 14:28:42 /mnt/share/work/2017-07-15_WAH yo dnsmasq[25359]: warning: no upstream servers configured Sep 27 14:28:02 yoyo dnsmasq[25359]: setting upstream servers from DBus Sep 27 14:28:02 yoyo dnsmasq[25359]: using nameserver 192.168.42.129#53(via eth0 Sep 27 14:28:02 yoyo dnsmasq[25359]: using nameserver 192.168.42.248#53(via eth0 Wed Sep 27 14:28:32 /mnt/share/work/2017-07-15_WAH