Connection between Infiniband Switches

Good evening,
I would like to know how to connect two infiniband switches to maximize the interconnection bandwidth.
I have an 8700 and 8790 switch. I want to connect two racks each with 20 nodes at 200gb/s. I would like to connect the two switches with 10/20 inifniband passive cables to have 2000gb/s of interconnection between the switches. Is it enough to connect the cables or do I have to set something at the software level on the 8700 switch? Which mode do you recommend to obtain this type of interconnection? Stacking or other?
Thanks
Matteo

Any suggestion?

Once you have a subnet manager running and the switches have physical connections – links should be up and running.

With regards to the BW question – assuming both switches have 40 ports, to obtain a none-blocking topology you would need 1:1 ratio of down/up links on each switch. So each switch may host 20 nodes while interconnecting with 20 ports to the other switch.
Any other configuration with 20 nodes hanging off the switch will cause a blocking scenario and won’t allow full line rate between nodes.

With regards to the configuration of the managed 8700 switch – none is needed in the simplest case of just connecting the ports to the 8790 link-partner. Unless the ports were previously configured to lower speeds, the default configuration should allow the switch to linkup in the highest rate the cable (I.e. 200gbps cable would raise 200gbps link etc.)

Hi dwaxman,
Thank you very much for the reply. The concept of blocking and connection is clear to me. How can I verify that for example if 5 nodes go at 200gb/s and connect to as many 5 nodes in the other rack, the bandwidth is actually 5x200gb/s? How do switches figure out which way to pass traffic? Is there a routing manager or something? Technically, am I sure it works without having to claim to use interconnect cables for stacking between switches?
Regards,
Matteo