Many systems and applications require certain access to certain ports and protocols. When installing these systems using Ansible it is necessary to also open up the needed ports so that the systems can function correctly. As there is no iptables module in Ansible the shell command is needed to add the iptables rules.
As an example, here is a task that adds a iptables rule to allow Apache to communicate on port 80.
- name: Apache | add apache iptable rule
command: /sbin/iptables -I INPUT 1 -p tcp --dport http -j ACCEPT -m comment --comment "Apache"
Once this is in place you might need to save and/or restart iptables in order to get the rule to be permanently saved. The following two rules will save the iptables rule and restart the iptables service. Note that these commands are specific to Ubuntu and so might not work on your system setup.