Tunnel between FreeBSD and Linux

bsd# nos-tun -t /dev/tun0 -s 192.168.0.1 -d 192.168.0.2 -p 4 IP2
bsd# ifconfig tun0 mtu 1500
bsd# ifconfig tun0 up

linux# modprobe ipip
linux# ip tunnel add tun0 mode ipip remote IP1 local IP2
linux# ifconfig tun0 192.168.0.2 pointopoint 192.168.0.1
linux# ifconfig tun0 up