2 LAN, 1 WAN with IPSEC tunnel - How to?

Hello,

More of a sanity check and looking for some good advice on how to properly set this up...

Currently have an Astaro V8 with three network interfaces configured as such:
WAN
LAN1 - Open access to WAN (limited filtering)
LAN2 - Unused, setting up a new LAN segment on this adapter intended for site to site traffic.

I would like to setup a site to site VPN tunnel and route all traffic from LAN2 over this connection without disrupting LAN1 users.

Conceptually I understand how this will work, however I'm looking for any advice or if there is an easy way to set this up I would like to know.

Thanks!