How a firewall works?

The firewall acts as the front end for receiving packets from remote servers. Whenever a request comes, it is first received at the firewall end:

The firewall will check its Rule table to see if a particular IP is allowed to connect to the remote Server on the specified Port.

If the rule is Allow, then the firewall will allow the packet to go inside; however, if it is denied, then the access is blocked.

There are three major sets in which rules are configured:

• Source IP address
• Destination port
• Rule (Allow or Deny)

If we look at the preceding diagram, the IP address starting from 52.24.52.24 is allowed to access the server on all the ports. However, 17.24.53.32 is allowed but only on Port 80 and 32.42.59.26 is not allowed at all.