Do a DNS query. You don't even have to randomise the id number, just query for something that will have a small set of results (so, not the root) and ensure checking is disabled. For 8.8.8.8, I'm guessing "dns.google" is probably an excellent target.
If you wanted something generic, what about a PTR query for something in 10/8, directed at the AS112 project? That's pretty much the sinkhole that expects that kind of unwanted traffic...
I bet that within a gnat's crotchet you'll find systemd has adopted that as a special "liveness" command or something. </snark>
M