I have been running a VPS which is situated in Amsterdam. It has not given any problems, and can be reached from most locations reliably.
Except when a French customer was not able to reach the server by IP. First I assumed their network was blocking the traffic. Layer, another customer in Germany started experiencing the same problem.
Finally I am able to reproduce the problem by attempt to connect to it from an AWS EC2 instance (the problematic server is not hosted on AWS). From the EC2 instance I can not access my VPS in Amsterdam in any way. Traceroute ends somewhere in Denmark at 193.202.110.243.
Interestingly, when doing a tracroute from the French customer to the IP, the traffic also ends at exactly that IP.
By "not reachable in any way", I mean any connections on port 80, 442, 22 as well as ICMP packets directed at the IP, all time out with no response. The server can be reached on all these ports from all locations except the three problematic ones mentioned.
There are no firewalls active on my VPS, but the hosting provider might be blocking the traffic, of course.
What can cause such inconsistent reachability of a host?
