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Does a Successful Ping Mean Port 443 Is Reachable? Diagnosing Server Connectivity

CiscoSoftware Engineer · Onsite
EasySoftware EngineerOnsiteSoftware Engineering Fundamentals

Last updated

A networking fundamentals question asking whether a successful ping to a server proves that port 443 on it is accessible, and how to check the port directly. It tests the difference between ICMP and TCP, the role of firewalls and listening services, and practical connectivity troubleshooting with command-line tools.

If you can successfully ping a server, does that mean port 443 on that server is accessible? Explain why or why not, and describe how you would find out whether port 443 is actually reachable from your machine.

Clarifying Questions

  • Is there a firewall, cloud security group, NAT gateway or load balancer between the client and the server?
  • Does "accessible" mean that a TCP connection can be opened, or that the HTTPS service on that port responds correctly?
  • Is the question about reachability from one particular client network, or from anywhere on the internet?

Hints

Hint 1

Compare the two kinds of traffic: Work out which protocol carries a ping and which carries a connection to port 443, and whether the devices along the path treat the two the same way.

Hint 2

List what must be true: Write down everything that has to work for a client to complete an HTTPS connection to that port, then mark which of those items a ping actually exercises.

Follow-up questions

  • Ping to the server fails, but HTTPS to it works. How is that possible?
  • A TCP connection test to port 443 times out from your laptop but succeeds from a machine in the server's subnet. What do you suspect, and how do you confirm it?
  • The TCP connection to port 443 opens, but the browser reports a certificate error. Is the port accessible?
  • How would you turn this check into an automated health check that a test pipeline runs?