How to do IKE site-to-site properly?

Hi all,

I'm trying to set up a VPN tunnel between the SRX220 and a remote server. The server runs Ubuntu and StrongSwan providing IKEv2 VPN service (with server certificate and EAP username/password client authentication)

The VPN works well on iOS clients. Now, I want to configure the SRX so that all traffic from the internal network (SRX side) gets routed through the VPN tunnel.

Any advice on how to do this?