b0x# kldstat
Id Refs Address Size Name
1 5 0xc0400000 34f898 kernel
2 14 0xc0750000 56270 acpi.ko
3 1 0xc0c97000 1c000 ipl.ko
4 1 0xc15ef000 4000 if_gre.ko

# kldload if_gre.ko
# sysctl -w net.inet.ip.gre_default_mtu=1450
# ifconfig gre1 create
# ifconfig gre1 tunnel 217.154.12.2 212.25.240.34
# ifconfig gre1 mtu 1450
# ifconfig gre1 inet 10.1.12.38 10.1.12.37 netmask 255.255.255.252
# ifconfig gre1 up

And that was that!

or Lan :

# ifconfig gre1 inet 10.1.12.37 10.1.12.38 netmask 255.255.255.252 up
# /usr/sbin/greconfig -i gre1 -v -s 212.25.240.34 -d 217.154.12.2