Rstp Port Redundancy; Mstp Operation - Siemens RX1500 User Manual

RUGGEDCOM ROX II
User Guide
For more information, refer to the RUGGEDCOM White Paper Performance of the RSTP in Ring Network
Topologies available on www.siemens.com/ruggedcom.
6. Decide upon a port cost calculation strategy.
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. Disable RSTP Fast Root Failover option.
This is a proprietary feature of Siemens. In ROX II, the RSTP Fast Root Failover option is enabled by default.
It is recommended to disable this feature when operating in a Ring network.
8. Implement the network and test under load.
Section 5.34.2.3

RSTP Port Redundancy

In cases where port redundancy is essential, RSTP allows more than one bridge port to service a LAN. In the
following example, if port 3 is designated to carry the network traffic of LAN A, port 4 will block traffic. Should an
interface failure occur on port 3, port 4 will assume control of the LAN.
Figure 819: Example - Port Redundancy
Section 5.34.3

MSTP Operation

The Multiple Spanning Tree (MST) algorithm and protocol provide greater control and flexibility than RSTP and
legacy STP. MSTP (Multiple Spanning Tree Protocol) is an extension of RSTP, whereby multiple spanning trees
may be maintained on the same bridged network. Data traffic is allocated to one or several spanning trees by
mapping one or more VLANs to the network.
The sophistication and utility of the MSTP implementation on a given bridged network is proportional to the
amount of planning and design invested in configuring MSTP.
If MSTP is activated on some or all of the bridges in a network with no additional configuration, the result will
be a fully and simply connected network. At best though, the result will be the same as a network using only
RSTP. Taking full advantage of the features offered by MSTP requires a potentially large number of configuration
variables to be derived from an analysis of data traffic on the bridged network, and from requirements for load
sharing, redundancy, and path optimization. Once these parameters have all been derived, it is also critical they
are consistently applied and managed across all bridges in an MST region.
RSTP Port Redundancy
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Chapter 5
Setup and Configuration
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