18
User Guide
Link Loss Carry Forward (LLCF)
*
The R642-xx and R612-51 line cards incorporate LLCF for 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.
The diagram below shows a typical network configuration with a good link
status using Radiance line cards for remote connectivity. Note that LLCF is
enabled as indicated in the diagram.
Management
Station
Management
Station
Switch/Hub
w/SNMP
Switch/Hub
w/SNMP
Radiance
Line Card
Radiance
Line Card
LED lit = established link
LED unlit = no link
LLCF is ON
LLCF is ON
Remote
Cable
If a connection breaks, the line cards carry that link loss forward to the switch/
hubs which generate a trap to the management stations. A network administrator
can then determine the source of the problem.
Link Loss Carried Forward
Link Loss Carried Forward
LED lit = established link
LED unlit = no link
Management
Station
Management
Station
Switch/Hub
w/SNMP
Switch/Hub
w/SNMP
Radiance
Line Card
Radiance
Line Card
LLCF is ON
LLCF is ON
Broken
Remote
Cable
Link Loss Carried Forward
LED lit = established link
LED unlit = no link
Management
Station
Management
Station
Switch/Hub
w/SNMP
Switch/Hub
w/SNMP
Radiance
Line Card
Radiance
Line Card
LLCF is ON
LLCF is ON
Broken
Cable
Remote
Cable
Important: When connecting a line card with LLCF enabled to an auto-
negotiating device, force both sides of the configuration to 10Mbps and either
full or half duplex. This allows the line card to immediately see link pulses and
start passing data.
* Units are shipped with LLCF disabled (OFF).
