L2TP/IPSec VPN server on /16 network

Every example I can find showing how to configure an L2TP/IPSec VPN service on a MT router uses a /24 as the network behind the VPN server.
This is for a “road warrior” type setup, not a site-to-site VPN.
My VPN service works perfectly, provided I only want to reach 192.168.1/24 which is the same /24 as the MT router itself is in (it’s at 192.168.1.1).

My home network is all over 192.168/16. I have routes up and working nicely on the MT that tell it how to reach all the rest of 192.168/16 (via a couple of Layer 3 switches).

When my VPN client connects, the client automatically adds a route for 192.168.1**/24** to its routing table.
How can I make the MT tell the client that it needs to add the route for 192.168**/16** and not 192.168.1/24?

The client I’m testing with happens to be a Mac, but I want to avoid having any “special” config on each client.

I’m running the latest 4.40.1(?) stable release, as of today 17 Aug 2017.

Any ideas how I do this please?

Thanks! Jules.