How do you check for open ports on a network?

Using a port scanning tool like Nmap is an effective way to check for open ports on a network because it employs various techniques to send packets to specified ports and analyzes the responses. With this information, it can determine which ports are open, closed, or filtered, thereby giving a clear indication of the network's security posture. Nmap is widely used by IT professionals for network discovery and security auditing, making it a reliable choice for this task.

Port scanners can scan a range of IP addresses, offering insights into the devices that are actively listening for connections and those that might be vulnerable to attacks. This method is efficient and allows for automated checking across multiple devices, which manual methods would struggle to match in terms of speed and thoroughness.