User Manual

Understanding backhaul loopback testing
IP-RN 8000 Installation & Commissioning Guide 159
Understanding backhaul loopback testing
Loopback testing each backhaul link verifies the backhaul installation was performed correctly and verifies
physical layer operation before the technician leaves the site. During manufacturing the backhaul interfaces
are loopback tested to the punch block, ensuring all internal components function properly. Loopback testing
during installation can be performed to verify the correct wiring into the punch block and the external
physical infrastructure.
The extent of the loopback test (the amount of equipment and cabling that is tested) depends on where the
physical loop back is installed. The farther away from the node the loop back is installed, the greater the
extent of the test.
Airvana recommends installing the loopback at least as far as the far end of each backhaul cable exiting the
cabinet. Installation at that point includes the backhaul cable’s wiring into the backhaul punch block and the
backhaul cable itself.
The technician must have appropriate equipment and materials for installing and performing loopbacks.
NOTE
The loop back testing described here does not include backhaul
circuits, only physical layer functionality at the cell site.
Backhaul circuits must undergo end-to-end testing and
acceptance at the time they are brought up by the service
provider.
NOTE
Ethernet loopbacks cannot be installed at the far side of a router,
switch, FRAD, or other edge device.
NOTE
Maximum cable lengths must be considered when installing
loopbacks. Loopbacks double the length of a cable (the cable
length now equals the outgoing leg plus the return leg, or twice
the physical cable length). Failure to consider this factor can
result in failed loopback tests for cables that are flawless.