Just a correction here, on SRX5400 we have to use port 0 only as the device only have 1 RE. Apologies for sharing incorrect information.
Note
SRX5000 line devices do not have built-in ports, so the control link for these gateways must be the control ports on their Services Processing Cards (SPCs) with a slot numbering offset of 3 for SRX5400, offset of 6 for SRX5600 devices and 12 for SRX5800 devices.
When you connect a single control link on SRX5000 line devices, the control link ports are a one-to-one mapping with the Routing Engine slot. If your Routing Engine is in slot 0, you must use control port 0 to link the Routing Engines.