Today I accidentally discovered, that I can ping addresses in the
172.31.0.0/16 subnet and get an ICMP reply. I tried a few random ones, it always got replies. After checking the routing table and a tentative
traceroute,it looks like the associated packets are leaving my local network, i.e. leaving towards my ISP. My local network uses a different IP range, part of the
192.168.0.0/16 subnet and there are Docker-related interfaces for
172.19.0.0/16, but not
It was my understanding that
172.31.0.0/16 should still be part of the of the
172.16.0.0/12 IANA-reserved address space.
I tried a web search to see whether the range of this subnet might have been shortened due to global IP address shortage or any other reason but couldn't find anything to support that hypothesis.
Now I'm wondering whether I'm just lacking some sleep and overlooking something elementary or whether there's something seriously borked in my networking setup.