On 21/12/2023 12:00, peter.northerly@gmail.com wrote:

ifconfig gives this: enp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 > inet6 fe80::d2da:494:eadc:4e0b prefixlen 64 scopeid 0x20<link> ether 08:60:6e:e7:d2:be txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) > RX errors 0 dropped 0 overruns 0 frame 0 TX packets 982 bytes 158082 (154.3 KiB) TX errors 1 dropped 0 overruns 0 carrier 0 collisions 0

I'm suspicious of the complete lack of received packets there. It appears you are sending (probably DHCP requests), but getting nothing back. Things to check:

1/ The cable - swap out for a known working one (from another PC?) 2/ The sockets - dust bunnies cause havoc ;-) 3/ Everything other than the affected machine - pop a different device on the end of the cable if you have one (or borrow one!) 4/ The kernel message log (/var/log/kern.log and/or dmesg) might be shouting about something unwell. 5/ Recent software changes (updates perchance? new kernel?), can you roll back (kernel - most likely you can pick previous at boot)

(more advanced detective work)

6/ Fire up a packet sniffer (tshark, wireshark) and watch for packets going in/out of the device on the affected machine. 7/ If you have a network *hub* (NOT a switch), then pop that in line and use another machine to watch for packets to/from the MAC address (I'd use tshark or wireshark, YMMV) on another port of the hub.

My money is on a recent kernel change borking receive or dust bunnies.

Phil.