IPSec tunnel between Juniper SRX and pfSense Firewall

How to set up an IPsec tunnel between a pfSense Firewall and a Juniper vSRX firewall. PfSense is a leading open source firewall distribution. Junos vSRX is Juniper’s firewall or security router. In this article we go into how to configure site to site VPNs between the two different vendors.