OpenVPN can ping both peers, but I can't reach any of the other machines on the remote subnet.

• Make sure that the firewall is not filtering the TUN/TAP interface.

• Make sure you have IP forwarding enabled on the server.

• If you are using routing (not ethernet bridging), ensure the clients (or LAN gateway) have a route back to the server for the packets coming in over the tunnel. This can be achieved by:

  • Adding a route in your default gateway for the VPN network IP subnet pointing to the OpenVPN machine,
  • Adding a route to every client, or
  • NATing all VPN traffic to the local address of the OpenVPN machine for network traffic which leaves the OpenVPN machine for the local net.

• If you are hosting the OpenVPN server on an Amazon Web Services (AWS) EC2 instance, make sure "Source/Destination Checking" is disabled on the instance's Elastic Network Interface (enabled by default).

• If you are still stumped, use tcpdump, wireshark, or WinDump to determine where packets are being dropped.