[windexh8er]

Tailscale shouldn't advertise a route that is local to the machine. This is a routing loop. The way SR route distribution works in Tailscale is that you accept all routes or nothing. Routing platforms have the concept of route filters to prevent accepting an advertised route that would create a loop.

There are hacky ways around this without having to deal with metrics (just advertise a /23 instead of a /24 and the /24 will be selected by default). But if you've got contiguous subnets you may not be able to clobber the additional address space just to avoid the route.

[RockRobotRock]

I really thought Tailscale would automagically figure this out. If this were true in all cases, my internet would not work at all since it would try to reach my router through the Tailscale interface.

It's odd.

[windexh8er]

The SR can't route for your gateway or else Tailscale itself would break it's own connection. A gateway IP isn't treated the same as a subnet route.

[readyplayeremma]

You don’t have any specific routes to random internet addresses though. And Tailscale would not either. Unless your Windows server is running BGP, all your Internet traffic is hitting the default route.