The next goal is to make the two Gl.inet routers (Opal and Slate AX) connect via “site to site”

Had tried in the past, tried it again now I get the following:

-Both router’s have a public IP: I believe they both have. Opal through ISP router and Slate AX through a Huawei 4G mobile router (E5788).

-Port 51830: I guess I have to open this port to both ISP and E5788 router?

-Router behind NAT: I guess both Opal and Slate are behind NAT’s right? so I have to setup port (51830) forwarding?