User guide

Metrobility “redundant twister” 19
Management
Station
Management
Station
Switch/Hub
w/SNMP
Switch/Hub
w/SNMP
“redundant twister”
2711
“redundant twister”
2711
Cable
Connection
LED lit = established link LED unlit = no link
Management
Station
Management
Station
Switch/Hub
w/SNMP
Switch/Hub
w/SNMP
“redundant twister”
2711
“redundant twister”
2711
Broken
Cable
Connection
Link Loss Carried
LED lit = established link LED unlit = no link
Link Loss Carry Forward (LLCF)
The “redundant twister” 2711-11 has been designed with a LLCF function for
troubleshooting a remote connection. The unit is shipped with the LLCF disabled.
When LLCF is enabled, the twisted-pair ports on the “redundant twister” do not transmit
a link signal until they receive a link signal from the opposite port. For example, if
LLCF is enabled and two “redundant twister” units are connected via a twisted-pair
cable with nothing else connected to them, the Link LED does not illuminate. When a
valid link is established at the twisted-pair port, a complete connection is accomplished.
The diagram below shows a typical network configuration using a “redundant
twister” for remote connectivity:
If the connection breaks, or the device fails, the “redundant twister” carries that link
loss all the way to the switch/hub which generates a trap to the management station.
The administrator can then look at the “redundant twister” to determine the source of
the loss.
IMPORTANT: When connecting a “redundant twister” to a port that supports auto-
negotiation, it is strongly recommended to fix the port settings to 10Mbps and either
full or half duplex. This allows the “redundant twister” to sense receive link and
select the active port.