JDS Uniphase IP Video Test Option HST-3000, User Manual

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Chapter 3 Ethernet Testing
Loopback testing
90
HST-3000 Ethernet Testing User’s Guide
When using the automatic loopback feature, the HST must be
configured as follows:
– If you are looping back layer 2 traffic, the near end HST
automatically detects the MAC address for the next unit
on the circuit; therefore, you do not need to configure the
destination MAC address. It will be populated automati-
cally for you.
– If you are looping back layer 3 traffic, you must specify the
source IP address for the HST on the far end of the circuit
as the destination IP address for traffic transmitted by the
near end HST. Be certain to specify the same destination
address (link-local or global) for the filter on the receiving
unit and the traffic looped back by the unit on the far end.
– If you are looping back layer 3 MPLS traffic, received
frames are looped through to the transmitter after swap-
ping the Destination and Source MAC addresses. The
MPLS labels are replaced with the labels defined for the
loopback unit before the frames are looped through to the
transmitter of the loopback unit.
– If you are looping back layer 4 traffic, the destination port
number for the near end HST must be configured with the
source port number for the HST on the far end. After you
issue the Loop Up command, and the near end unit
receives a response from the unit on the far end indicating
that the loop up was successful, the near end unit’s ATP
Listen Port is automatically set to the destination port
number carried in the looped back traffic and cannot be
changed. The far end unit’s ATP Listen Port will also auto-
matically be set to the destination port carried in the traffic
it receives from the near end unit.
– You can optionally specify unit identifiers for each HST
(for example, “Joe_s HST” and “Sam_s HST”). When the
HSTs send confirmation messages to each other indi-
cating the status of the loopback, the message will identify
each HST using the identifier. For details on specifying a
unit identifier for your HST, see
“Specifying test mode and
network visibility settings” on page 30 .