#!/bin/sh
#
# GRE example.  Use at your own risk!
# 
# You'll need two of these (one for each end of the tunnel).  You should
# really only have to swap ThisEnd and OtherEnd, set a different InternalIP,
# and pick which networks you want to route for each side.  No other changes
# should be needed.
#
# If you're doing GRE tunneling with NoCatAuth, also be sure to clear the
# traffic through your gateway, or packets will just drop on the floor!
#
# The advanced router tools package (specifically ip) is required for this
# script.  Get it online here: ftp://ftp.inr.ac.ru/ip-routing/
#
# Assembled 7/30/02, by Rob Flickenger <rob@nocat.net>.  
#   This is Freeware.  Do something free with it.

#
# Set ThisEnd to the live, routed, "real" IP address on this end of the tunnel
#
ThisEnd="240.101.83.2"

#
# OtherEnd is the live, routed, "real" IP address of the other end
#
OtherEnd="251.4.92.217"

#
# Set InternalIP to any unused IP address on the same subnet as your
# internal interface
#
InternalIP="10.42.3.62"

#
# Give this tunnel a short, alphanumeric name
#
TunnelName="tunnel0"

#
# List all networks that you'd like to route down the tunnel here.
#
RemoteNets="10.42.2.0/26 10.42.5.0/26"

#
# That's it.  No user serviceable parts below!
#

PATH=/sbin:/usr/sbin:/usr/local/sbin:/bin:/usr/bin:/usr/local/bin

modprobe ip_gre

ip tunnel add $TunnelName mode gre remote $OtherEnd local $ThisEnd ttl 255
ip addr add $InternalIP dev $TunnelName
ip link set $TunnelName up

for net in $RemoteNets; do
  ip route add $net dev $TunnelName
done

echo "$TunnelName is up.  To bring it down again, try this:"
echo
echo "ip link set $TunnelName down"
echo "ip tunnel del $TunnelName"
echo
echo "Have fun..."

#
# Ende
#