GRE Tunnel confusion

Hey guys! I work for a WISP that has one static public IP address and we’ve natted our balance 580 over to our own static IP address scheme within our network. We have several clients using a number of VPN connections to
work from home and there is no problem. A new client of ours is trying to use a microsoft VPN connection and its saying something about a GRE connection. I found how to access the GRE tunneling feature, but now Im not sure as to what goes where in the setup. It first requires you to setup a new GRE profile. You first apply a name. Then a box is checked for “active.” Then you have three boxes to fill. Remote GRE IP address, Tunnel Local IP address, Tunnel Remote IP address. Then I can choose which WAN connection its on, and finally theres a section for Remote Networks with a box and a subnet mask dropdown menu, which in this section I can add or remove that last portion if its needed or not.

Ive dealt with port forwarding issues before and I dont feel like this is that kind of issue, but I was wondering if anyone had some thoughts on what goes where and what each means. Thank you!

GRE tunnel is still an experimental feature.
This post should should still be relevant if you like to find out more.

Other than that, similar to what your client has mentioned, simply saying something about a GRE connection isn’t enough. Will need more information than that.
However, based on what information you’ve shared so far, most of your clients use some form of outbound client-to-gateway connection. GRE is more of a gateway-to-gateway connection, similar to IPSec.

It’s been almost 5 months since the last post on that thread. Any updates on GRE moving from experimental to a more supported feature?

I’m afraid there’s still no visible ETA of it been a full-fledged feature yet, aside from what’s available right now.
As per the aforementioned thread, this remains more of a supply and demand thing.

I appreciate your help! Thank you!