general routing setup

setup_routes

#!/bin/bash
#assuming appliance is a dns server on another network
#and you want to be able to talk to those clients on that network
#and you can ssh into the appliance
#this might be useful if you dont want to use iptables

appliance="192.168.100.76"
route add -net 172.18.0.0 netmask 255.255.0.0 gw "$appliance"

ssh root@"$appliance" route add -net 172.18.0.0 netmask 255.255.0.0 gw 172.18.0.1; echo "1" > /proc/sys/net/ipv4/ip_forward;

#should you need to delete the route, use this:
route del -net 172.18.0.0 netmask 255.255.0.0