This document describe how to create IP-IP tunnel at linux box.
(for 2.4 kernel)


                eth0:192.168.1.1                   eth0:192.168.2.1
                eth1:10.0.1.1                      eth1:10.0.2.1
		tnl0:192.168.253.1/30              tnl:192.168.253.2/30       	       	       	       	       			  

	        [Router A](eth0)======//====== eth0[Router B]    	       	   
                   (eth1)                           (eth1)
                     |                                |
    10.0.1.0/24	     | 	       	       	              |    	10.0.2.0/24 
 ---+-----------+----+---		          ----+------+-----------+------
    |  	       	|      	   				     |           |      
   [Host]    [Host]				           [Host]      [Host] 
							       	       	   


[Router A]
# ip tunnel add tnl0 mode ipip local 192.168.1.1 remote 192.168.2.1
# ip addr add 10.0.253.1/30 dev tnl0
# ip link set tnl0 up
# ip route add 10.0.2.0/24 dev tnl0

[Router B]
# ip tunnel add tnl0 mode ipip local 192.168.2.1 remote 192.168.1.1
# ip addr add 10.0.253.2/30 dev tnl0
# ip link set tnl0 up
# ip route add 10.0.1.0/24 dev tnl0


($Karaba: MakingIPTunnel.txt,v 1.4 2004/01/16 03:00:53 mk Exp $)