Wired ethernet suddenly dropped. How to troubleshoot?

Jphillips · 2020-10-20 09:13:04

My computer has a wired ethernet connection behind a university firewall, using a fixed IP address. I left my computer on overnight and this morning the ethernet was down. From looking at the logs I cannot figure out what the issue is. Here's the relevant portion from last night up until this morning:

Oct 20 07:09:35 syscomp kernel: igb 0000:06:00.0 enp6s0: igb: enp6s0 NIC Link is Down
Oct 20 07:09:41 syscomp NetworkManager[666]: <info>  [1603170581.3655] device (enp6s0): state change: activated -> unavailable (reason 'carrier-changed', sys-iface-state: 'managed')
Oct 20 07:09:41 syscomp NetworkManager[666]: <info>  [1603170581.3772] dhcp6 (enp6s0): canceled DHCP transaction
Oct 20 07:09:41 syscomp NetworkManager[666]: <info>  [1603170581.3772] dhcp6 (enp6s0): state changed bound -> done
Oct 20 07:09:41 syscomp avahi-daemon[663]: Withdrawing address record for 127.311.112.215 on enp6s0.
Oct 20 07:09:41 syscomp avahi-daemon[663]: Leaving mDNS multicast group on interface enp6s0.IPv4 with address 127.311.112.215.
Oct 20 07:09:41 syscomp avahi-daemon[663]: Interface enp6s0.IPv4 no longer relevant for mDNS.
Oct 20 07:09:41 syscomp avahi-daemon[663]: Withdrawing address record for 2031:17b:9bc:1a12:5334::21 on enp6s0.
Oct 20 07:09:41 syscomp avahi-daemon[663]: Leaving mDNS multicast group on interface enp6s0.IPv6 with address 2031:17b:9bc:1a12:5334::21.
Oct 20 07:09:41 syscomp avahi-daemon[663]: Joining mDNS multicast group on interface enp6s0.IPv6 with address bc72::1b3a:111e:c1c1:bd12.
Oct 20 07:09:41 syscomp avahi-daemon[663]: Registering new address record for bc72::1b3a:111e:c1c1:bd12 on enp6s0.*.
Oct 20 07:09:41 syscomp avahi-daemon[663]: Withdrawing address record for bc72::1b3a:111e:c1c1:bd12 on enp6s0.
Oct 20 07:09:41 syscomp avahi-daemon[663]: Leaving mDNS multicast group on interface enp6s0.IPv6 with address bc72::1b3a:111e:c1c1:bd12.
Oct 20 07:09:41 syscomp avahi-daemon[663]: Interface enp6s0.IPv6 no longer relevant for mDNS.
Oct 20 07:22:21 syscomp kernel: igb 0000:06:00.0 enp6s0: igb: enp6s0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX
Oct 20 07:22:21 syscomp NetworkManager[666]: <info>  [1603171341.9679] device (enp6s0): carrier: link connected
Oct 20 07:22:21 syscomp NetworkManager[666]: <info>  [1603171341.9681] device (enp6s0): state change: unavailable -> disconnected (reason 'carrier-changed', sys-iface-state: 'managed')
Oct 20 07:22:21 syscomp NetworkManager[666]: <info>  [1603171341.9699] device (enp6s0): Activation: starting connection 'Wired connection 1' (e68cbcbb-59da-3891-b980-be23551f5032)
Oct 20 07:22:21 syscomp NetworkManager[666]: <info>  [1603171341.9700] device (enp6s0): state change: disconnected -> prepare (reason 'none', sys-iface-state: 'managed')
Oct 20 07:22:21 syscomp NetworkManager[666]: <info>  [1603171341.9708] device (enp6s0): state change: prepare -> config (reason 'none', sys-iface-state: 'managed')
Oct 20 07:22:21 syscomp NetworkManager[666]: <info>  [1603171341.9715] device (enp6s0): state change: config -> ip-config (reason 'none', sys-iface-state: 'managed')
Oct 20 07:22:21 syscomp avahi-daemon[663]: Joining mDNS multicast group on interface enp6s0.IPv6 with address bc72::1b3a:111e:c1c1:bd12.
Oct 20 07:22:21 syscomp avahi-daemon[663]: New relevant interface enp6s0.IPv6 for mDNS.
Oct 20 07:22:21 syscomp avahi-daemon[663]: Registering new address record for bc72::1b3a:111e:c1c1:bd12 on enp6s0.*.
Oct 20 07:22:21 syscomp avahi-daemon[663]: Joining mDNS multicast group on interface enp6s0.IPv4 with address 127.311.112.215.
Oct 20 07:22:21 syscomp avahi-daemon[663]: New relevant interface enp6s0.IPv4 for mDNS.
Oct 20 07:22:21 syscomp avahi-daemon[663]: Registering new address record for 127.311.112.215 on enp6s0.IPv4.
Oct 20 07:22:21 syscomp acvpnagent[692]: IP addresses from active interfaces: enp6s0: 127.311.112.215, BC72:0:0:0:1B3A:111E:C1C1:BD12
Oct 20 07:22:21 syscomp NetworkManager[666]: <info>  [1603171341.9792] device (enp6s0): state change: ip-config -> ip-check (reason 'none', sys-iface-state: 'managed')
Oct 20 07:22:21 syscomp NetworkManager[666]: <info>  [1603171341.9870] device (enp6s0): state change: ip-check -> secondaries (reason 'none', sys-iface-state: 'managed')
Oct 20 07:22:21 syscomp NetworkManager[666]: <info>  [1603171341.9873] device (enp6s0): state change: secondaries -> activated (reason 'none', sys-iface-state: 'managed')
Oct 20 07:22:21 syscomp NetworkManager[666]: <info>  [1603171341.9887] policy: set 'Wired connection 1' (enp6s0) as default for IPv4 routing and DNS
Oct 20 07:22:21 syscomp NetworkManager[666]: <info>  [1603171341.9889] device (enp6s0): Activation: successful, device activated.
Oct 20 07:22:26 syscomp acvpnagent[692]: Function: getDnsConfiguration File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1249 Unable to get domain list for interface enp6s0.
Oct 20 07:22:26 syscomp acvpnagent[692]: Function: getDnsConfiguration File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1249 Unable to get domain list for interface enp6s0.
Oct 20 07:22:41 syscomp acvpnagent[692]: Function: getDnsConfiguration File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1249 Unable to get domain list for interface enp6s0.
Oct 20 07:22:41 syscomp acvpnagent[692]: Function: getDnsConfiguration File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1249 Unable to get domain list for interface enp6s0.
Oct 20 07:23:06 syscomp acvpnagent[692]: Function: getDnsConfiguration File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1249 Unable to get domain list for interface enp6s0.
Oct 20 07:23:06 syscomp acvpnagent[692]: Function: getDnsConfiguration File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1249 Unable to get domain list for interface enp6s0.
Oct 20 07:23:41 syscomp acvpnagent[692]: Function: getDnsConfiguration File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1249 Unable to get domain list for interface enp6s0.
Oct 20 07:23:41 syscomp acvpnagent[692]: Function: getDnsConfiguration File: ../../vpn/Common/Utility/NetInterface_unix.cpp Line: 1249 Unable to get domain list for interface enp6s0.
Oct 20 07:25:04 syscomp NetworkManager[666]: <info>  [1603171504.9715] dhcp6 (enp6s0): activation: beginning transaction (timeout in 45 seconds)
Oct 20 07:25:04 syscomp NetworkManager[666]: <info>  [1603171504.9727] policy: set 'Wired connection 1' (enp6s0) as default for IPv6 routing and DNS
Oct 20 07:25:50 syscomp NetworkManager[666]: <warn>  [1603171550.6604] dhcp6 (enp6s0): request timed out
Oct 20 07:25:50 syscomp NetworkManager[666]: <info>  [1603171550.6604] dhcp6 (enp6s0): state changed unknown -> timeout

What the heck happened? I've tried various troubleshooting -- following the Arch wiki, and just doing basic stop/restart of services. Does this even look like an issue with my machine, or do the logs suggest it's an issue with the university DNS server or similar? Any other thoughts on how to go about troubleshooting?

solskog · 2020-10-20 11:23:37

Jphillips wrote:

using a fixed IP address

How is this "fixed" ip address assigned to you, it still looks like a dhcp release from your log.

$ ip add
$ ip route show

Jphillips · 2020-10-20 11:47:33

Thanks for the quick reply. The static ip is assigned based on mac address, and linked to a specific ethernet port. I originally configured it following the instructions on the Arch wiki for static IP. That being said, there certainly might be some conflict that I haven't fully resolved. Originally I was using wifi and dhcp, and this was created a big issue trying to dynamically assign the IP once I moved to a static Ip. I sorted that out and it's been fine for a year or so.

Here's the output you requested:

$ ip add
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    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
2: enp6s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 02:c7:b1:23:72:12 brd ff:ff:ff:ff:ff:ff
    inet 127.311.112.215/24 brd 127.311.112.255 scope global noprefixroute enp6s0
       valid_lft forever preferred_lft forever
3: enp5s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc fq_codel state DOWN group default qlen 1000
    link/ether 02:c7:b1:c4:23:55 brd ff:ff:ff:ff:ff:ff
4: wlp4s0: <BROADCAST,MULTICAST> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
    link/ether 31:71:66:12:b1:32 brd ff:ff:ff:ff:ff:ff permaddr 17:77:21:31:cc:42

$ ip route show
default via 127.311.112.1 dev enp6s0 proto static metric 100 
127.311.112.0/24 dev enp6s0 proto kernel scope link src 127.311.112.215 metric 100 
127.311.112.0/24 via 127.311.112.1 dev enp6s0 proto static metric 100

My IP is set up to use the MAC for enp6s0. I'm mostly confused why this would just stop working when I hadn't done anything to change the settings.

seth · 2020-10-20 12:16:37

How do you define "the ethernet was down"?
The initial log shows the carrier got cut (could very well be for a router reboot) and then gets re-established on the static IPv4 and then NM tries and fails to obtain an IPv6 address over dhcp.
The last output shows that enp6s0 is up, has a carrier, an IPv4 and the default route goes there.

=>
Can you still ping 8.8.8.8? google.com? Is this maybe an avahi-only issue?

For a static IP I'd btw. rather use something more simple, https://wiki.archlinux.org/index.php/Dh … ic_profile

solskog · 2020-10-21 03:53:29

seth wrote:

For a static IP I'd btw. rather use something more simple,

I agree, with dhcpcd OR systemd-networkd you could get rid of both avahi-daemon and NetworkManager.
https://wiki.archlinux.org/index.php/Sy … _static_IP

Jphillips wrote:

acvpnagent[692]: IP addresses from active interfaces: enp6s0:

Is this a standalone service?

Arch Linux

#1 2020-10-20 09:13:04

Wired ethernet suddenly dropped. How to troubleshoot?

#2 2020-10-20 11:23:37

Re: Wired ethernet suddenly dropped. How to troubleshoot?

#3 2020-10-20 11:47:33

Re: Wired ethernet suddenly dropped. How to troubleshoot?

#4 2020-10-20 12:16:37

Re: Wired ethernet suddenly dropped. How to troubleshoot?

#5 2020-10-21 03:53:29

Re: Wired ethernet suddenly dropped. How to troubleshoot?

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