OpenVPN w/BR500 and Static IP

Check  ifconfig-push

„Push virtual IP endpoints for client tunnel, overriding the –ifconfig-pool dynamic allocation.” https://openvpn.net/index.php/open-source/documentation/manuals/65-openvpn-20x-manpage.html

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–ifconfig-push local remote-netmaskPush virtual IP endpoints for client tunnel, overriding the –ifconfig-pool dynamic allocation.The parameters local and remote-netmask are set according to the –ifconfig directive which you want to execute on the client machine to configure the remote end of the tunnel. Note that the parameters local and remote-netmask are from the perspective of the client, not the server. They may be DNS names rather than IP addresses, in which case they will be resolved on the server at the time of client connection.

This option must be associated with a specific client instance, which means that it must be specified either in a client instance config file using –client-config-dir or dynamically generated using a –client-connect script.

Remember also to include a –route directive in the main OpenVPN config file which encloses local, so that the kernel will know to route it to the server’s TUN/TAP interface.

OpenVPN’s internal client IP address selection algorithm works as follows:

1 — Use –client-connect script generated file for static IP (first choice).
2 — Use –client-config-dir file for static IP (next choice).
3 — Use –ifconfig-pool allocation for dynamic IP (last choice).

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Correct in that the OpenDNS setting configured within the BR500 OpenVPN page would not help -- as that is set to the external (Internet / WAN) IP of the BR500.

However, it looks like on the client side of OpenVPN -- which in my case is a Linux server -- there is a '--ipchange {command}' option, which will run a named script or command, passing the IP address assigned.  I could have this update a different DynDNS name, separate from the BR500's external name, with the IP address that has been assigned by the BR500's OpenVPN server.

There are also 'up' (and 'down') scripts that can be referenced in the client configuration file, which run a script when an OpenVPN connection is brought up (down).  Again, these could be used to update a DynDNS name (separate from the external name of the BR500).

Or, perhaps a bit more daring, even run a remote script to edit the /etc/hosts file(s) of the LAN server(s) with the IP assigned to the Linux server.  This is a bit more brute force, but gets around DNS caching (although I could set the DNS TTL as low as 1 min).

Nonetheless, probably cleaner to do on the OpenVPN server side buy dropping a configuration file into the CCD (Client Configuration Directory?) which matches the client -- and also provides a lot more options, like specifiing a route command -- but alas, I don't know how to drop a file into the /etc/openvpn/ccd directory of the OpenVPN server running within the BR500 (although since the BR500 if running Linux, I know it is there!).