Troubleshooting client-to-client traffic routing

In this recipe, we will troubleshoot a VPN setup where it is the intention that client-to-client traffic is enabled, but the server configuration directive "client-to-client" is missing. In a TUN-style network, it is possible to allow client-to-client traffic without this directive and it even allows the server administrator to apply firewalling rules to the traffic between clients. In a TAP-style network, this is generally not possible, as will be explained in the There's more... section.

Getting ready

We use the following network layout:

Set up the client and server certificates using the first recipe from Chapter 2, Client-server IP-only Networks. For this recipe, the server computer was running CentOS 6 Linux and OpenVPN 2.3.11. The first client was running Fedora 22 Linux and OpenVPN 2.3.11. The second client was running Windows 7 64bit and OpenVPN 2.3.11. Keep the configuration file basic-udp-server.conf from the Server-side routing recipe...