vtun

virtual tunnel over TCP/IP networks
VTun is the easiest way to create virtual tunnels over TCP/IP networks
with traffic shaping and compression.
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It supports IP, PPP, SLIP, Ethernet and other tunnel types.
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VTun is easily and highly configurable, it can be used for various
network tasks.
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VTun requires the universal TUN/TAP kernel module which can be found at
http://vtun.sourceforge.net/tun/index.html or in the 2.4 and newer Linux
kernels.
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Note: This program includes an "encryption" feature intended to protect the
tunneled data as it travels across the network. However, the protocol it uses
is known to be very insecure, and you should not rely on it to deter anyone
but a casual eavesdropper. See the included README.Encryption file for more
information.