How to connect three routers?

[BadGad]

Hello, would please someone explain me how to connect R1 to R2 ? and R1 to R3? The connection has to be ethernet.
What network they should belong to ?
Thank you !

 

[BadGad]

obvliously I will have to put more details...
I was thinking to assign 172.16.0.0 - 172.31.255.255 (172.16/12 prefix) (RFC1918) which gives me 16 supernets 1048574 addresses each with but would this causes me any trobles in the future?
for example:
R1-172.16.4.1
R2-172.16.8.1
R2-172.16.12.1
so that I can add hosts to each of those three new nets
And if I add the default route 172.16.0.0 in the route table would this work in this way?
I haven't tried to implement supernets so far
or it will be more beneficiall if I just set defaul class c addresses like
R1 - 192.168.0.1 and 192.168.1.1
R2 - 192.168.0.2
R3 - 192.168.1.2

I just cannot figure it out how the route table would look like in this way