12.0 Loopback
The loopback application in the main menu allows the user to establish a manual loopback on the test set. The loopback function
is used when an end-to-end test needs to be performed with one of the test partners in software loopback mode. The loopback
function will loop back the incoming traffic to the test set back into the network under test.
The type of traffic that the loopback function loops back will depend on the type of test layer configured (Layer 1, 2, 3, or 4).
Additional criteria can be set to allow only messages with specific criteria to be looped back. To specify loopback parameters,
select the desired parameter and choose Enable from the drop-down menu. Tap on the box and input a value or select one of the
drop-down menu choices:
Layer 1
: All incoming traffic to the Rx loopback interface will be sent out unaltered to the Tx loopback interface.
Layer 2, 3, & 4
: In a Layer 2 or 3 loopback all incoming test traffic will be looped back.
The loopback function will swap the MAC destination and MAC Source addresses (for Layer 2) or MAC and IP
destination and source addresses (for Layer 3).
All incoming frames with CRC errors will be dropped, similar to what an Ethernet switch does.
All broadcast and multicast frames will be dropped including any incoming unicast frames that have the MAC Source
address equal to the MAC Destination address.
Loopback Parameters
: The following parameters are available on Layer 2, 3 and 4. For more information on the
parameters, please see
in the BERT section. It is possible to enable any of these parameters
to create a customer loopback filter. For example, if you enable a filter with VLAN 64, Priority 7, only traffic
corresponding to these values will be looped back.
VLAN ID
VLAN Priority
MAC Source
MAC Destination
IP Source Address (Layer 3 & 4 only)
IP Destination (Layer 3 & 4 only)
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