Routing traffic between two networks with iptables

I you have not enabled iptables just activate ip forwarding :)

# sysctl -w net.ipv4.conf.all.forwarding=1


Most Linux distributions enable filtering by default so you'll have to do it using iptables

# iptables -I FORWARD -i eth0 -o wlan0 -s wi.red.net.work/24 -d wire.less.net.work/24 -j ACCEPT
# iptables -I FORWARD -i wlan0 -o eth0 -s wire.less.net.work/24 -d wi.red.net.work/24 -j ACCEPT

References