Configuring Link Speed on UCS 6545 Fabric Interconnects as 10/25G ports is not at all intuitive. You would think that right-clicking on a port under Equipment > Fabric Interconncets > Fabric Interconnect A (or B) |> General would give you the option to change the links speed (it does for 40G ports, but not 10/25G ports)
So the secret is to double-click on the port to bring up the Properties window.
From here you find the Show Interface option, and once that is opened, you can find the Admin Speed setting.
Imagine calling the option “Show Interface” rather than “Configure Interface”.