User's Manual

RuggedSwitch™ User Guide
2. Identify required legacy support and ports with half duplex/shared media
restrictions.
These bridges should not be used if network failover/recovery times are to be
minimized.
3. Identify edge ports
Ports that connect to host computers, IEDs and controllers may be set to edge ports in
order to guarantee rapid transitioning to forwarding as well as reduce the number of
topology change notifications in the network.
4. Choose the root bridge.
The root bridge can be selected to equalize either the number of bridges, number of
stations or amount of traffic on either of its legs. It is important to realize that the ring
will always be broken in one spot and that traffic always flows through the root
5. Assign bridge priorities to the ring.
The strategy that should be used is to assign each bridge’s priority to correspond to its
distance from the root bridge. If the root bridge is assigned the lowest priority of 0,
the bridges on either side should use a priority of 4096 and the next bridges 8192 and
so on. As there are 16 levels of bridge priority available, this method provides for up
to 31 bridges in the ring.
6. Implement the network and test under load.
RSTP Port Redundancy
In cases where port redundancy is essential, RSTP allows more than one bridge
port to service a LAN. For example if port 3 is designated to carry the network
traffic of LAN A, port 4 will block. Should an interface failure occur on port 3,
port 4 would assume control of the LAN.
Figure 36: Port Redundancy
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