A configuration I have used at a number of locations is to have a router on one ISP with my inside default gateway address and at another part of the campus a router connected to a second ISP with a unique inside address.  The secondary is used for testing and in case of failure of the primary ISP or issues at that location we can change the IP on the secondary unit and continue to function.

I tried to set this up in OMADA and it will not allow me to connect the second ER7206.  Am I doing something wrong or is this by design?  This is a very useful feature for the redundancy and also in a multibuilding campus if you have a failure of the link between building then both can have some level of connectivity.

Any ideas would be appreciated.