In safari, and several other products, I get a network timeout where I have to reload the page, even though I have a full / working Wifi connection.

This is a sporadic issue.

The problem seems to occur after I installed Cisco's security product "OpenDNS Umbrella". Removing OpenDNS Umbrella seems to fix the problem.

I would like to get a better understanding of the network layers in macOS so I can create an appropriate trace/diagnostic for review.

  1. What are the "layers" of software that are available for extension and modification in macOS? (I'm from a Windows Mindset and understand MSFT's well-documented network API, packet filters, and what extensions are available etc).

  2. How can I create a trace of network activity at the aforementioned layers? For example, I want to see not just DNS traces, but any internal firewall that could be affecting me? (macOS has a built-in firewall that might be giving me trouble.)

I did briefly install "Little Snitch" firewall program, but I then uninstalled it. I'm not sure if this is relevant, but it does manage connections via an API I'm not aware of.

  • System Preferences > Security & Privacy > Firewall. If it's off there, there is no firewall (from a built-into-macOS perspective) active.
    – tubedogg
    Oct 4 '16 at 16:07
  • @tubedogg - the Gui firewall is off. Issue remains. Oct 4 '16 at 19:44

Try to install Wireshark. Maybe monitoring the actual network activity will give you a clue (it will probably show an outgoing packet or connection that isn't answered).

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