check if this is enabled or not by
sudo iptables -t nat -L If There are any entries , delete them using:
sudo iptables -F -t nat Try without src dest flags:
sudo iptables -t nat -A PREROUTING -p tcp --dport 30 -j REDIRECT --to-ports 1234 check again if this is enabled or not by
sudo iptables -t nat -L It is Important to remove chained entries queued by default to "OUTPUT" route.
Hope This helps!!