L
ON
W
ORKS
Router User’s Guide
2-3
•
Support for Open Media
. Open media such as RF may require redundant routers
with overlapping coverage to ensure complete coverage of an area.
Configured routers can be used to support looping topologies, by configuring the routers
to prevent message loops. For example, the topology in figure 2.1 can be supported if
both routers are configured to forward all messages addressed to subnets on channel B
from channel A; and all messages addressed to subnets on channel A from channel B.
Any groups with members on both channels can only be forwarded by one of the two
routers.
Network services tools such as the LonMaker Installation Tool or custom tools based on
the LonManager API can automatically set up the forwarding tables for configured
redundant routers.
Power Line Routers
A looping topology can be inadvertently created when using power line media.
Passive coupling between different phases of a power line system can cause packets
transmitted on one phase to be received by nodes installed on another phase. A loop
can be formed when active coupling provided by a router is combined with passive
coupling. Figure 2.2 illustrates an example looping topology.
Phase A
to Phase B
Router
Power Line Phase A
Power Line Phase B
Passive
Coupling
▲
▼
▼
▼
Figure 2.2
A Looping Topology with One Router
Routers can be used between power line channels only if the two channels are fully
isolated. This is generally not the case between two phases on the same circuit, but
may be the case between phases on different distribution transformers. Echelon’s
PLCA-10, PLCA-20, or PLCA-30 Power Line Communication Analyzers should be used
to confirm isolation between power line channels before installing power line to power
line routers.
Summary of Contents for LONWORKS
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