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The problem: 2 nodes, let's call them client and server - connected through VPN. Server runs a daemon (a game in a LAN hosting mode), the client cannot see/discover it as a local server while direct connections work. It is common to all games tried so it appears it's not a game question but a networking question. The vast majority of games cannot operate without discovering local hosts so this becomes a crippling problem.

Parameters of the situation and things that have been tried:

  • nodes connected via VPN
  • ping OK
  • the VPN virtual adapters are correctly set to the highest priority (Networking - Games can't see/join anyone else's LAN servers, unless I host)
  • tried disabling all other adapters
  • server is ok, tested with another client on the same VPN network, so VPN infrastructure checks out as well
  • tested with all client-side firewalls disabled on both client and server, negative
  • same with anti virus on both, disabled, negative
  • all connections are wired
  • tried alternative VPN although it checked out OK with another client, as expected, no change. Works with client2 but doesn't work with client1.
  • tried another client (client3) on the exact same network as the original problematic client, everything checked out OK!

Direct connect works, broadcasting seems to work (since test with client2 is OK) this exact same setup with client1 used to work weeks ago, notable parameters of the situation:

  • same hardware, both computer and networking
  • one difference, client changed OS from Windows 7 to Windows 10
  • the test client (client2) runs Windows 10 as well and it tested OK, discovered and connected successfully, all that with firewall on both server and client, works fine (the setup really is fine).

Suspicion is the problem lies with the client. Running out of ideas, any suggestions?

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Packet analysis helped me get to the bottom of it. I figured I'd post a reply in case someone else runs into similar problems, solution could save them a lot of time and potential stress. Should it be kept in the form of an answer?

Cause: The problematic machine was dropping incoming broadcast. Guessing w10 drivers. What added to the confusion was - outgoing broadcast traffic was normal.

Solution: Alternative NIC circumvents the problem completely.

Hardware in question: Asus P8H61-M Pro

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