I'm having difficulty working out the details of standing up a second site using a site to site VPN.

Currently I have Site A which has the following:

ER7206 -  gateway

OC200 - Hardware controller

Multiple EAP245

I will be setting up a new Site B using a ER605 as the gateway.

So far, I've managed Site A using OC200 controller with the Omada interface through the cloud.  Now I need to setup Site B with the intent of using the same controller from Site A.  In order to adopt the hardware from Site B to the hardware controller which is physically in Site A, I need to setup a site-to-site VPN connection between my gateways from Site A and Site B correct?  And I will need to set this up using the router interface for my ER7206 gateway on Site A, and the settings directly on my router ER605 in site B correct?  Once I'm able to establish a connection - the OC200 on Site A will be able to adopt the hardware on Site B correct?

Once all the hardware is adopted, will the VPN that was setup previously directly in the routers be visible in Omada?  

Just looking for a high level order of proceedure in doing this to save some headaches.

Thanks!!