pfSense

OpenVPN does all the ifconfig stuff of setting up the interface, so pfSense doesn't have to, but there are a couple of niggles with it when assigning the interface.

Assuming you have a typical 'topology net30' OpenVPN connection, you will have for example 10.0.0.140/30 as the local tunnel end point and 10.0.0.141/30 as the remote tunnel endpoint, with a /30 subnet so traffic can communicate between the two. However, the gateway will reside outside this subnet, say 10.0.0.254, and is configured via a static route through 10.0.0.140 or 141 (can't remember which) to get to the gateway IP. As such when configuring a tun device as an interface with a static IP, can you ensure that it will accept the gateway as part of a /24 subnet and not a /30 subnet?