I want to link my and my parents’ networks using Zerotier.
My network is 10.0.1.x/24
Their network is 10.0.0.x/24
Neither routers are extremely modern, so router-based VPNs are not an option. I have multiple old laptops that I can use on either ends, though.
I’ve followed the Layer 2 Bridge to configure a laptop on my network as a bridge, and can access my 10.0.1.x network from any device with Zerotier on.
However, I realized while I was doing this that I’m assigning IPs in my 10.0.1.x subnet to the Zerotier interfaces. I suspect that when I repeat the process on their 10.0.0.x subnet, I’m going to have issues reaching devices behind the Bridge IP Address.
You can do this, but you’re working with L3, not L2. If you wanted to use the same subnet on both sites, then you would use the L2 bridging. You will definitely want to set a route between Zerotier and Physical networks. Given that you can’t install Zerotier on the existing routers, this is a little more complicated since you need to communicate a way to route between the subnets via your Zerotier enabled laptops.
So on your network you need a zerotier enabled machine, say 10.0.1.253. On the existing router, you add a static route stating that the destination network of 10.0.0.0/24 is via the router at 10.0.1.253. On the Zerotier side you configure a managed route using the Zerotier address of the machine on the second site as the destination for 10.0.0.0/24.
And all of the same inversed to get traffic flowing in the other direction.
This may require some futzing with firewall rules and stuff so the other option would be to add the static routes to the individual machines (either manually or via DHCP) so that they go directly to the zerotier machine instead of using the default route.
You’re just dealing with the central side of the infrastructure so the Mikrotik stuff is irrelevant, but the linking of their two sites is exactly what you’re trying to accomplish