Metrobility 10/100 AutoTwister 17
Auto-Recovery
A typical application of the 10/100 AutoTwister is to use it in pairs to extend a net-
work’s reach between two distant devices.
Switch/Hub
w/SNMP
Switch/Hub
w/SNMP
AutoTwister
AutoTwister
LED lit = established link
LED unlit = no link
Fiber
Cable
In this back-to-back setup, it may be desirable to see the entire link down if any of
the connecting segments fails. This means that both copper ports must relay a no link
condition to the switch/hub when any of the cables is broken.
For proper operation in this configuration, auto-recovery must be enabled. In the
standalone AutoTwister, auto-recovery is enabled only when all of the following
switches are set as indicated:
AN1 = disabled (OFF)
LLR2 = enabled (ON)
LLCF = enabled (ON)
Because LLR is enabled on both units, auto-recovery is required to prevent the two
fiber ports from ending up in a deadlock situation, with each waiting for the other to
transmit first. Auto-recovery allows the deadlock to be broken by periodically send
-
ing out pulses from the fiber port forcing the AutoTwister to establish its fiber link if
the line is intact.
The diagrams below show how the two switch/hubs are alerted to a broken fiber
cable. Notice that both LLR and LLCF must be enabled under this condition.
Switch/Hub
w/SNMP
Switch/Hub
w/SNMP
AutoTwister
AutoTwister
LED lit = established link
LED unlit = no link
Fiber
Cable
Link Loss
Carried Forward
Link Loss
Returned
Link Loss
Carried Forward
Switch/Hub
w/SNMP
Switch/Hub
w/SNMP
AutoTwister
AutoTwister
LED lit = established link
LED unlit = no link
Fiber
Cable
Link Loss
Carried Forward
Link Loss
Returned
Link Loss
Carried Forward
