Starting 

Start isakmpd: isakmpd -K

Load the ipsec flows: ipsecctl -f /etc/ipsec.conf

Load pf-rules: pfctl -f /etc/pf.conf

Making it stick:

Edit /etc/rc.conf.local

         isakmpd_flags="-K"
         pf=YES
         ipsec=YES

Edit/etc/sysctl.conf

         net.inet.ip.forwarding=1