METRObility Optical Systems RADIANCE 10/100MBPS ACCESS OPTICAL NETWORK UNIT - Manual (Page 17)

Radiance 10/100Mbps Access Optical Network Unit 17
Link Loss Carry Forward (LLCF) *
The Access Optical Network Unit incorporates Link Loss Carry Forward as an
aid in troubleshooting a remote connection. When LLCF is enabled, the ports do
not transmit a link signal until they receive a link signal from the opposite port.
Warning: If LLCF is enabled on the Access ONU and its copper port loses link,
you will be unable to manage the ONU. Only enable LLCF when notification of
a link loss is more important than remote management functionality.
The diagram below shows a typical network configuration with a good link
status using a Radiance Access Line Card and an Access ONU for remote
connectivity. Note that LLCF is enabled as indicated in the diagram.
Management
Station
Switch/Hub
w/SNMP
Customer
Site
Access
Line Card
Access
ONU
LED lit = established link LED unlit = no link
LLCF is ON LLCF is ON
TX TX FX
Remote
Cable
If a connection breaks, as shown below, one or both line cards will carry that
link loss forward to the switch/hub which generates a trap to the management
station. The administrator can then determine the source of the problem.
Link Loss Carried Forward
LED lit = established link LED unlit = no link
Management
Station
Switch/Hub
w/SNMP
Customer
Site
Access
Line Card
Access
ONU
LLCF is ON LLCF is ON
TX TX Broken
FX Remote
Cable
Link Loss Carried Forward
LED lit = established link LED unlit = no link
Management
Station
Switch/Hub
w/SNMP
Customer
Site
Access
Line Card
Access
ONU
LLCF is ON LLCF is ON
TX Broken
TX
Cable
FX
Remote
Cable
Important: When connecting an Access ONU with LLCF enabled to an auto-
negotiating device, force both sides of the configuration to the same duplex and
speed. This allows the unit to immediately see link pulses and start passing data.
*The unit is shipped with LLCF disabled (OFF).