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Chapter 5
Setup and Configuration
2.
Identify required legacy support.
Are STP bridges used in the network? These bridges do not support rapid transitioning to forwarding. If these
bridges are present, can they be re-deployed closer to the network edge?
3.
Identify edge ports and ports with half-duplex/shared media restrictions.
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 to reduce the number of topology change notifications in the
network. Ports with half-duplex/shared media restrictions require special attention in order to guarantee that
they do not cause extended fail-over/recovery times.
4.
Choose the root bridge and backup root bridge carefully.
The root bridge should be selected to be at the concentration point of network traffic. Locate the backup root
bridge adjacent to the root bridge. One strategy that may be used is to tune the bridge priority to establish
the root bridge and then tune each bridge's priority to correspond to its distance from the root bridge.
5.
Identify desired steady state topology.
Identify the desired steady state topology taking into account link speeds, offered traffic and QOS. Examine
of the effects of breaking selected links, taking into account network loading and the quality of alternate links.
6.
Decide upon a port cost calculation strategy.
Select whether fixed or auto-negotiated costs should be used? It is recommended to use the auto-negotiated
cost style, unless it is necessary for the network design to change the auto-negotiated cost style. Select
whether the STP or RSTP cost style should be used. Make sure to configure the same cost style on all
devices on the network.
7.
Enable RSTP Fast Root Failover option.
This is a proprietary feature of Siemens. In a mesh network with only RUGGEDCOM devices in the core
of the network, it is recommended to enable the RSTP Fast Root Failover option to minimize the network
downtime in the event of a Root bridge failure.
8.
Calculate and configure priorities and costs.
9.
Implement the network and test under load.
Section 5.36.2.2
RSTP in Ring Backbone Configurations
RSTP may be used in ring backbone configurations where rapid recovery from link failure is required. In normal
operation, RSTP will block traffic on one of the links, for example, as indicated by the double bars through link H
in
Figure
15. In the event of a failure on link D, bridge 444 will unblock link H. Bridge 333 will communicate with
the network through link F.
520
RUGGEDCOM ROX II
CLI User Guide
RSTP in Ring Backbone Configurations
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Table of Contents
Troubleshooting
