The Great Port Mystery: Why Ping Doesn't Play by the Rules

It’s a question that has stumped many a budding network engineer and curious tech user: “What port does ping work on?” We’re so used to associating every network service with a specific port number, web pages with 80/443, SSH with 22, email with 25, that it feels like a trick question.

And in a way, it is. The answer is simple, surprising, and fundamentally important: ping doesn’t use any port at all. None. Zero. Nada.

The Two-Tiered Network Universe

To understand why, you have to picture the internet as a multi-layered system, almost like a building with different floors.

• Upstairs (The Transport Layer - Layer 4): This is where TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) live. These are the protocols that handle application-to-application communication. They use port numbers as a sort of apartment number within a server. When your web browser asks for a website, it's a TCP request to a specific port, say port 443. That port directs the request to the correct application on the web server.

• Downstairs (The Network Layer - Layer 3): This is the foundation of the network. It's where the IP (Internet Protocol) lives, and its only job is to get a packet from one IP address to another, no matter where they are in the world. This layer doesn’t care about applications or ports; it just cares about getting the data to the right building address.

ping operates exclusively on this ground floor. It uses a different protocol entirely, one that also lives at Layer 3 alongside IP: ICMP (Internet Control Message Protocol).

ICMP: The Network’s Humble Messenger

Think of ICMP as the network’s silent, behind-the-scenes janitor. It's not here to carry your data; it's here to deliver status updates about the network itself. Its messages are simple and direct:

• “Hey, are you there?” (The ICMP Echo Request that ping sends).

• “Nope, that address is unreachable.”

• “The packet is too big!”

When you run ping 8.8.8.8, your computer sends a small ICMP Echo Request packet to Google’s server. If the server is up and its firewall allows ICMP traffic, it sends back an ICMP Echo Reply. That's it. There are no TCP or UDP headers, which means there's no space for a port number. The ping command is a network health check, not a conversation with a specific service.

Here's an example of the command you'd run:

ping 8.8.8.8

The "Pinging a Port" Mix-Up

This is why we get confused. We've all used tools like telnet or netcat to check if a specific port is open, and we often describe this action as "pinging a port."

For example, running nc -vz example.com 80 is a common way to test for a web server. But under the hood, this is a TCP connection attempt to a specific port. It's like asking for a specific person by name. A true ping is just a general check to see if anyone is home.

Here are the commands you might see for this kind of check:

# Using Netcat to check for a TCP connection on port 80
nc -vz example.com 80

# Using Telnet to check for a TCP connection on port 22 (SSH)
telnet example.com 22

This distinction is crucial for troubleshooting.

• If ping works but your application can’t connect, it means the host is reachable, but the specific application's port is blocked by a firewall or the service is down.

• If ping fails but your application can connect; it means your network is blocking ICMP traffic, which is common on security-hardened networks.

Knowing the difference between a network-layer check and a transport-layer check can save you hours of head-scratching and turn you into a network troubleshooting pro.

References:

What port does 'ping' work on?