Hi, with a clever series of Jumping that could be possible. Not sure about it being supported by Core Tunnel.
A - host in private lan with B.
B - host connected to the private lan of A as well as, let’s say the internet.
C - host connected to the internet and a private lan together with D
D - host connected to a private lan with C
The goal is to connect from A to D.
Configuration should be all on host A:
connection to D with ProxyCommand “ssh C -W %h:%p”
connection to C with ProxyCommand “ssh B -W %h:%p”
connection to B without a proxy command.
Use the IP/hostnames as the host that is the proxy can reach it.
As explained, this is how it should work with plain openssh. Not sure if that setup is possible in Core Tunnel.