Figure 98: L-IP Redundant with Bus Loop Monitoring.
Now the L-IP Redundant is able to detect a cable fracture by permanently comparing the
traffic on both sides of the bus: If the L-IP Redundant sees different traffic on its two
terminals, the cable is deemed to be broken. In this case it starts to duplicate the traffic from
loop port 1 to loop port 2 and vice versa. Further an alarm is issued (see Sections 9.5.5 and
9.6.3). Once messages are received on both sides again the ring is considered closed and the
cable fracture is deemed gone.
The L-IP Redundant is shipped with bus loop monitoring enabled. If bus loop monitoring is
not desired it must be switched off to avoid a permanent “Ring open” alarm. Bus loop
monitoring parameters can be configured using the L-IP Redundant plug-in (see Section
9.5.7) or the web interface (see Section 9.6.5).
The current bus loop monitoring state can be determined via network variables (see Section
9.7), in the L-IP Redundant plug-in (see Section 9.5.3), and in the web interface (see
Section 9.6.1).
Important: To guarantee proper function of the bus loop monitoring algorithm it is required to keep
average bandwidth utilization on the monitored segment below 50%! Bandwidth
utilization can be monitored using the LOYTEC LPA or the built in diagnostic functions
(see Sections 9.5.4 and 9.6.1).
9.2.2 Router Redundancy
If IP network redundancy is available, full redundancy on the IP-Channel (Backbone) can
be achieved with two devices installed in parallel (see Figure 99). In this case router
redundancy is ensured as well by mutual monitoring of paired L-IP Redundant routers.
Since two L-IP Redundant routers are used in this scenario, this use case is sometimes also
referred to as “twin router mode”.
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