Background: I depend on a number of static IPv4 routes on my High Sierra machine, which I add using the
route command, and usually have to re-add only when moving the machine between different physical networks. But starting a week or two ago, these routes started spontaneously disappearing from the routing table at irregular times.
What macOS settings or network behavior would cause manually-added routes on macOS to be spontaneously dropped from the local IP routing table?
My primary suspect was DHCP, but I've switched to static IP assignment and the behavior persists.