VTun Setup recommendations and Config samples.

1. General recommendations:
1.1 IP tunnel
    type tun;
    proto udp;
    keepalive yes; 
    up {
       ifconfig "%% xxxxxxx";
    };
  This will give you reliable and the fastest possible Point-to-Point
  tunnel.  Use this tunnel type whenever it's possible, especially
  if performance and efficiency is concerned. If you need compression,
  use LZO or TCP protocol and ZLIB. 

1.2 Ethernet tunnel
    type ether;
    proto udp;
    keepalive yes; 
    up {
       ifconfig "%% xxxxxxx";
    };
  This will give you reliable and fast Ethernet tunnel. You can tunnel
  any protocol that works with Ethernet IP, IPX, Appletalk, DECnet, etc
  If you need compression, use LZO or TCP protocol and ZLIB. 

1.3 PPP or SLIP tunnel
    type tty;
    proto tcp;
    keepalive yes; 
    up {
       ppp "xxxxxxxxxxx";
    };
  This will give you reliable and fast PPP or SLIP tunnel. 
  You can safely use compression. 

1.4 Anything else :))
    type pipe; or type tty; if it depends on TTYs
    proto tcp;
    keepalive yes;
    up {
       program /xx/xx "yyyyy";
    } 
  Never use UDP with 'pipe' tunnel type. VTun allows it, but it is not 
  a good idea. Compression, encryption and shaping are safe for almost
  everything.

2. Configuration samples.
2.1 Example 1. 
We have to create virtual tunnels between 3 private IP networks in 
different locations on the Internet. All networks are being serviced 
by Linux boxes having dedicated links and a fixed IP address to the 
Internet. 
Network addresses and servers: 
   192.168.0.0 - Server S1 
   192.168.1.0 - Server S2
   192.168.2.0 - Server S3
We can setup S1 as a VTun server for S2 and S3 and create 3 tunnels.
But in this case we'll get a star net topology with unreliable and 
inefficient routing. That's why we will create 6 tunnels, each server 
will have two tunnels with other servers. 
S1 will have only server config, S2 will have server and client 
config and S3 only client config.

Here are VTun configs for each server:
Server S1
   default {
	type tun;
	proto udp;
	comp lzo:1;
	keepalive yes;
   }

   # Tunnel between S1 and S2 (192.168.0.0 <-> 192.168.1.0)
   # Server entry
   s2 {
	pass XXXX;
	up {
	   ifconfig "%% 192.168.0.1 pointopoint 192.168.0.2";
	   route "add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.0.2";
	   program /sbin/arp "-sD 192.168.0.2 eth0 pub";
	};
   }

   # Tunnel between S1 and S3 (192.168.0.0 <-> 192.168.2.0)
   # Server entry
   s3_1 {
	pass XXXX;
	up {
	   ifconfig "%% 192.168.0.1 pointopoint 192.168.0.3";
	   route "add -net 192.168.2.0 netmask 255.255.255.0 gw 192.168.0.3";
	   program /sbin/arp "-sD 192.168.0.3 eth0 pub";
	};
   }
   Start vtund as 'vtund -s'

Server S2
   default {
	type tun;
	proto udp;
	comp lzo:1;
	keepalive yes;
   }

   # Tunnel between S2 and S1 (192.168.1.0 <-> 192.168.0.0)
   # Client entry
   s2 {
	pass XXXX;
	up {
	   ifconfig "%% 192.168.0.2 pointopoint 192.168.0.1";
	   route "add -net 192.168.0.0 netmask 255.255.255.0 gw 192.168.0.1";
	};
   }

   # Tunnel between S2 and S3 (192.168.1.0 <-> 192.168.2.0)
   # Server entry
   s3_2 {
	pass XXXX;
	up {
	   ifconfig "%% 192.168.0.2 pointopoint 192.168.0.3";
	   route "add -net 192.168.2.0 netmask 255.255.255.0 gw 192.168.0.3";
	};
   }
	
   Start vtund as 
   'vtund -s'
   'vtund s2 real_address_of_s1'

Server S3
   # Tunnel between S3 and S1 (192.168.2.0 <-> 192.168.0.0)
   # Client entry
   s3_1 {
	pass XXXX;
	up {
	   ifconfig "%% 192.168.0.3 pointopoint 192.168.0.1";
	   route "add -net 192.168.0.0 netmask 255.255.255.0 gw 192.168.0.1";
	};
   }

   # Tunnel between S3 and S2 (192.168.2.0 <-> 192.168.1.0)
   # Client entry
   s3_2 {
	pass XXXX;
	up {
	   ifconfig "%% 192.168.0.3 pointopoint 192.168.0.2";
	   route "add -net 192.168.1.0 netmask 255.255.255.0 gw 192.168.0.2";
	};
   }
   
   Start vtund as
   'vtund s3_1 real_address_of_s1'
   'vtund s3_2 real_address_of_s2'