On some FortiGate models, you are being asked to connect a self-loopback cable on some ports during the HQIP test. This request looks like the following CLI output:
Network Interface Loopback Test - Please connect ethernet cables: WARNING: This test can only pass with factory configurations. Please restore factory reset or use port mode to perform the test [WAN1 - SELF-LOOPBACK] [WAN2 - Any of PORT1...PORT5] To skip this test, please press 'N'.
Even though the name «self-loopback» is for some people a bit confusing, this is a very common and standardized wiring method for testing copper based ethernet equipment.
Those cables are often descibed as selfloop or interface test cables. In comparison to normal «loopback» links, where one NIC is connected with another NIC on the same appliance, the self-loopback does realize the loopback inside the same NIC.
It is very easy to create a self-loopback cable or connector plug by yourself. You just need a RJ45 connector or an Ethernet cable with a RJ45 connector attached.
In the case of the FortiGate HQIP test, it’s already enough to connect the following conductor wires:
pin 1 <-> pin 3 pin 2 <-> pin 6
This is the simpliest version of a four pin self-loopback plug which is used to test interface rx/tx operations on FastEthernet (100mbit/sec) interfaces.
If you want to use your plug on appliances from other manufacturers too, that maybe need a higher throughput during testing, it may be needed to create an eight pin self-loopback plug. Those are used to test interface rx/tx operations on GigabitEthernet (1gbit/sec) interfaces. In this case, you need to connect two more wire pairs:
pin 1 <-> pin 3 pin 2 <-> pin 6 pin 4 <-> pin 7 pin 5 <-> pin 8
An example of a self-made self-loopback cable:
In this case we used an old Ethernet Cable, removed the cable isolation coat and connected the wires as described above. At the end, we put a heat shrink tubing around it to prevent any short circuits.
It looks best when served with fresh veggies on a silver plate. Bon appetit!