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Wireless Hacks by Rob Flickenger

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Using vtun over SSH

Connect two networks together using vtun and a single SSH connection.

vtun is a user space tunnel server, allowing entire networks to be tunneled to each other using the tun universal tunnel kernel driver. Using an encrypted tunnel such as vtun allows roaming wireless clients to secure all of their IP traffic using strong encryption. It currently runs under Linux, BSD, and Mac OS X. These examples assume that you are using Linux.

The procedure described next will allow a host with a private IP address (10.42.4.6) to bring up a new tunnel interface with a real, live routed IP address (208.201.239.33) that works as expected, as if the private network weren’t even there. Do this by bringing up the tunnel, dropping the default route, then adding a new default route via the other end of the tunnel.

To begin with, here is the (pretunneled) configuration of the network:

root@client:~# ifconfig eth2
eth2 Link encap:Ethernet HWaddr 00:02:2D:2A:27:EA 
inet addr:10.42.3.2 Bcast:10.42.3.63 Mask:255.255.255.192
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:662 errors:0 dropped:0 overruns:0 frame:0
TX packets:733 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100 
RX bytes:105616 (103.1 Kb) TX bytes:74259 (72.5 Kb)
Interrupt:3 Base address:0x100 

root@client:~# route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 10.42.3.0 * 255.255.255.192 U 0 0 0 eth2 loopback * 255.0.0.0 U 0 0 0 lo default 10.42.3.1 0.0.0.0 ...

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