In networking, the term “default gateway” is really misleading. How Cisco often refers to it, as the “gateway of last resort,” is far more accurate. That’s because this route is not really the “default.” If there is a directly connected network or a more specific route, the network traffic will follow that path.

Thus, the “default gateway” is only “default” in the sense that’s where traffic goes if there is nowhere else obvious for it to route.

I’ve blown many less experienced IT folk’s minds by having a Windows machine with no default gateway that could still access everything it needed to just fine. With specific routes, a default gateway is not required. You can even run OSPF on Windows with RRAS, if you really want to. (That said, Windows networking is weird and does many non-standard things, so expect that when you start monkeying with it.)