#!/bin/bash

echo "#!/bin/sh" > /root/tcp-rulesets1

exec 11</root/iprange1
exec 12</root/portrange1

while read -u 11 fip ; do
        read -u 12 prange1
echo "iptables -t nat -A PREROUTING -p udp -d <external ip here> --dport $prange -j DNAT --to-destination $fip" >> /root/tcp-rulesets1
done < /root/iprange1

exec 11<&- 12<&-