What a waisted day.
My DSL-CPE elected to reboot itself every three or four minutes. Ping packets run as usual initially, with 44ms RTT into the office, then times ramp into the hundreds, thousands, ... and between 10000ms and 20000ms the CPE reboots.
It's a lowly Fritz!Box 7130 operated just as an ADSL2+ modem, not as router. (FritzBoxen do a forced NAT. I run public IP space at home.)
Turning the machine of for a short (10 min) or long (5 hours) period didn't change anything. However, since exactly(!) midnight everything was OK again.
Let' see how this develops. I had just a single reboot today. A matching replacement power-supply is at hand, too: my small 5" VGA LCD monitor delivers 12V/1A, too. (Hey, 1.2A even.)
Thanks to my friendly upstairs neighbor who let's me use her WLAN & internet connection in times like these.
And yes: It's always a good idea to choose something other than the default vendor LAN addresses. Being connected both to my neighbor's WLAN 192.168.178.0/24 and on the LAN side to my CPE's 192.168.178.0/24 managment LAN just doesn't cut it.
Makes me wonder: can we already use the IPv6
fe80:...%if notation for RFC-3927
169.254.0.0/16 IPv4 link-local nets?