With the Eleven Rack, you have a few options depending on the outputs you want to use. You can bypass the cab manually, you can set the cab to always be OFF, or you could use an Output to Amp port and set the source to AMP OUTPUT (which is split off before the cab).
Here's a video that will go through all the options and consequences of bypassing the cab.
Keep in mind, whenever you BYPASS the cab, it is bypassed for ALL outputs, even the Mains/USB.
If you want the full rig through the Mains/USB, but only the amp sound (before cab) to run into an Amp/Cab at the same time, then you would not want to bypass the cab, but instead choose AMP OUTPUT for one/both of the Output To Amp ports.