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I have my Pi set up as an ownCloud server. I have port forwarding enabled on my router for two specific ports (one for SSH one for HTTPS), and the Pi is configured to accept these requests on these ports. Both of these services ran perfectly until a few months ago. Suddenly, I could not access the Pi externally, despite having made no changes to any Pi or router configurations. I have not had physical access to the Pi or router until now.

I can log into the Pi via SSH on the specified port from within my network. The issue now is that the logs in /var/log do not date back far enough to the time this issue began so I cannot view the auth, apache, sys, fail2ban, or user logs. When I connect to the Pi, I can confirm it has external access as I can ping google.com, curl icanhazip.com etc. with no issues.

Again, I did not change any settings on my router or Pi prior to this change occuring. I have since updated all packages in attempt to eradicate the error but it did not work. I am really lost. Can anyone provide me with some guidance?

Edit for clarification
When I try to access the machine via SSH using the domain name, the error I get is a timeout. When I ping the address of the domain name, I get the error "Destination host unreachable".

Update
Interestingly, the public IP address listed when I ping the domain name of the Pi is not the same as the one provided when I run "curl icanhazip.com" while logged into the Pi. Using the IP address provided by icanhazip.com, I can succesfully log into the Pi remotely. Does this mean that my domain settings have been misconfigured somehow?

Final update
This issue is solely to do with my own carelessness in not renewing my domain name, not a result of misconfigurations, firewalls, port forwarding etc.

  • It is impossible to say much about this unless you describe exactly what happens when you try to connect via 1) SSH, 2) A web browswer. – goldilocks Oct 5 '16 at 18:32
  • @goldilocks I have updated my question to clarify what you asked and have made an interesting discovery in the process. I would appreciate if you could take a look at it for me – Briscoooe Oct 5 '16 at 18:53
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When I try to access the machine via SSH using the DNS name, the error I get is a timeout.

There are two ways for that to happen:

  1. There is no machine at the resolved IP address, although there is a known route which should reach it if it is online.

  2. The machine at the address is using (or behind) a firewall that drops the packets. This is an unconventional thing for a firewall to do, because it creates more traffic for the machine running the firewall, since innocent applications will keep retrying until they time out. The normal way for a firewall to respond is with an ICMP packet saying the access is prohibited.

    However, it is still something a firewall can do if someone configures it to do so.

Something which will not cause this is if the machine is reachable, but the SSH server isn't running. That will generate an immediate response from the operating system on the machine reported as "connection refused" by SSH clients.

When I ping the address of the domain name, I get the error "Destination host unreachable".

I believe this has two different potential causes, although it's something I'm less sure about than the time out:

  1. At some point the request is turned around by a machine where there is no known route to the destination.

  2. A firewall is blocking the request.

This is a strange contrast that could I guess be explained by a firewall dropping packets in the first case and refusing them in the second, although I am sure there are other explanations besides that.

However, one thing that is for certain is unless you've configured a firewall to drop incoming SSH requests, they are never reaching the pi.

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