In which case:

  $ ping 127.0.0.1

I run a lot of pfSense boxes and they (and OPNSense) have a pinger daemon to test connectivity which is really useful for multi-link routing. Bad idea for single links because you add an extra thing to fail. On a router with multiple internet links they are handy. You mostly ping known "reasonably stable" anycast addresses - they are the best option and usually end up being DNS servers - 1.1.1.1, 8.8.8.8, 8.8.4.4 etc are all good candidates.