I have 2 RB1100AH one Site A and one Site B, I have 2 wireless link from A to B one with 17GHz the second with 2 5GHz Groove this for backup.
Which is the best solution for using 5GHz as backup of the 17GHz link? I thinking about bridge with RSTP or OSPF.
With bridge and rstp I can decide the priority of the port, but I prefer bridge with switch hardware of RB1100, and I can't find nothing about priority.
Thanks

RSTP is really designed more for loop prevention than selecting a forwarding path. It can be configured to do so, but OSPF is really better suited to select the best path between the two.

Unless you understand spanning tree extremely well, I would recommend against tuning spanning tree cost

Ok. I want to use main link everytime, and switch as fast as possible to backup in case of heavy rain and 17 GHz link down

You can tune the OSPF dead timer down to 2 to 3 seconds and rely solely on that, or ypu can couple that with BFD and get your failover time down into the milliseconds. BFD requires careful tuning to avoid constant route flapping but is well worth the effort.

BFD seem perfect for my main backbone link , because I need to reduce the down time as maximum as possible.
I'll looking for that.
Tanks

Another option can be Bonding?

My main backbone is this:

                _____(24GHz)_______>        _____(17GHz)_______>
GW---SiteA                                 SiteB                                SiteC----Network
                ---------(5GHz)--------->        --------(5GHz)--------->

Link ag is only beneficial if the links are of identical speed and latency. If they are different speeds, you can actually make it run slower than if they were independent.

If you do choose to test bonding, use LACP (802.3ad) as it will manage the bundling and traffic hashing

Ok, like I show my link are different 24/17GHz high bandwith this is the main link and 5GHz only for backup/failover.

What are the speeds of those backhauls?

The 24GHz is AirFiber (700MbitFD) but for me is ok 384Mb, and 17GHz is Siae and is around 400Mbit.
I need a bandwith tranfer from 350 to 400Mb