It’s rectangular and definitely an SFP+ connector, 4 of them in fact and there’s 2 of these controllers, so a total of 8 SMP+ connectors. It’s datacenter equipment so it’s designed to connect to an array of these 12 drive enclosures.
EDIT: It plainly shows that the connection is a 6GB connection. 6GB is far better than the 1gb the network used to be, so it’s not that bad.
Here’s a pic from the back (in my rack) showing the controller.
Regarding the router inbetween the switches, I expected the server to figure out a connection path dynamically. It turns out that TrueNAS works best if you reboot the system, something that for several months I could not do remotely. When I TrueNAS CORE was installed on my server, it did something to the BIOS, preventing me from setting the boot drive. For all those months I was forced to go to the server itself, then press the boot select button (F8) during the boot process and manually select the actual boot drive. That made me not as willing to reboot the system after every network change, but I eventually figured out the problem preventing the bios issue (reset the bios) and discovered I could connect the 2 switches, bypassing the router completely. Yes, I had this successfully work in the past, but because rebooting TrueNAS was so frustrating, I didn’t reboot the system when changes were made, making me think the system required the router inbetween them…