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I have a network of machines around the country, connecting via https to a cloud-based server through cellular modems.
Only one machine has a problem connecting. When I run nmap -p 443 <server_ip> on that machine, The result is “filtered.” The same command on any other machine results in “open.”
I have confirmed that the modem and machine is configured identically to the good ones: No difference in the firewall, port filtering or other internet settings.
What else could be blocking traffic from one machine, but not others?
Update: I reset the modem, which assigned it a different dynamic IP, and then the https port was open again. It appears that some hop along the chain was blocking HTTPS requests from that particular IP (dynamic from the provider). Is there any way to find who was blocking me?
AShelly
Posted 2015-02-19T17:01:24.977
Reputation: 369
Can you access the server from the problematic system by other means? I.e., can you access port 80 on the system, successfully ping it, or traceroute to it? – moonpoint – 2015-02-19T17:17:26.113
yes, I can access port 80. Ping is blocked for everyone. – AShelly – 2015-02-19T18:23:04.357