I have a Raspberry Pi 3 board and a CentOS 7.4 box both running libreswan-3.25. I want to connect the 2 using ipsec BUT I don't want to build a VPN (no L2TP/IPsec). I just want peer-to-peer communication minus tunneling. Are there instructions for this? Every web search I've done results in discussions of L2TP/IPsec (i.e., tunneling).