(Network Simulator) Configuring iptables firewall for a business network question

Hey everyone,

I'm setting up a business network in a network simulator but there's one thing I don't understand. I want to allow traffic only from the internal network and it works well when I allow access to specific subnets but how can I allow access to the whole network in the same command?

E.g. iptables -A FORWARD -i eth0 -p http -s 112.143.98.0/24 --destination-port 80 -j ACCEPT

So when I replace -s with 112.143.0.0/24 it doesn't work anymore. And I tried 112.143.00.0/24 with the same result. But everything I've found in google says to do it this way.

Am I missing something? Any help is much appreciated.