How do I allow firewall rules in Linux?

Example Firewall Rule to Allow Incoming SSH Connections

1. Delete Existing Rules. If you already have some iptables rules, take a backup before delete the existing rules. …
2. Allow only SSH. Allow only the incoming SSH connection to this server. …
3. Drop all Other Packets. …
4. View the SSH rule and Test.

How do I change the firewall rule in Linux?

Summary :

1. List the current rules of iptables: sudo iptables -L.
2. To change the default policy: …
3. To clear/flush all the rules. …
4. To append a rule at the end of the chain: …
5. To append a rule at the start of the chain: …
6. To implement a ACCEPT rule:- …
7. To implement a DROP rule:- …
8. Implementing rules on specific ports/protocols:-