A good way to figure out if there is a device blocking traffic to our servers is to run a telnet to a specific port. This won't always tell you what exactly is interfering with the traffic but will let you know that something in the path is dropping the traffic. It's also an integral part of how OpenDNS support does troubleshooting and you may be asked by support personnel to perform these steps.
A TCP "traceroute" run to a domain on a specific port should give a good idea as to where the traffic is being dropped. A traceroute simply shows the 'path' on the Internet between the host where the traceroute is run and the destination that's specified as well as where, if anywhere, the route is failing to complete. For instance, if you cannot reach foo.com from your computer, you can use tcptraceroute to map the path between your computer and the public website to see where along the line the problem is occurring.
References:
https://support.opendns.com/hc/en-us/articles/227989007-How-to-Running-a-TCP-Traceroute
A TCP "traceroute" run to a domain on a specific port should give a good idea as to where the traffic is being dropped. A traceroute simply shows the 'path' on the Internet between the host where the traceroute is run and the destination that's specified as well as where, if anywhere, the route is failing to complete. For instance, if you cannot reach foo.com from your computer, you can use tcptraceroute to map the path between your computer and the public website to see where along the line the problem is occurring.
References:
https://support.opendns.com/hc/en-us/articles/227989007-How-to-Running-a-TCP-Traceroute
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