Specifications

Configuring STP and RSTP
March 14, 2011 Page 11 of 29
Figure 6 Example of Multiple Regions and MSTIs
Configuring STP and RSTP
ThissectionprovidesinformationaboutthefollowingSpanningTreetasks:
• ReviewingandEnablingSpanningTree(page11)
• AdjustingSpanningTreeParameters(page12)
• EnablingtheBackupRootFunction(page16)
• AdjustingRSTPParameters(page16)
Reviewing and Enabling Spanning Tree
Bydefault,SpanningTreeisenabledgloballyonEnterasysswitchdevicesandenabledonall
ports.Onallswitchingdevices,thedefaultSpanningTreeversionissettoMSTP(802.1s)mode.
Table 3 MSTI Characteristics for Figure 6
MSTI / Region Characteristics
MSTI 1 in Region 1 Root is switching device 4, which is also the CIST regional root
MSTI 2 in Region 1 Root is switching device 5
MSTI 1 in Region 2 Root is switching device 7, which is also the CIST root
MSTI 1 in Region 3 Root is switching device 11
MSTI 2 in Region 3 Root is switching device 12
Switching device 10 is the CIST regional root
Region 1
12
34
5
Region 3
89
10 11
12
Region 2
6
7
Master Port Master Port
CIST
Regional Root
CIST Root
and CIST
Regional Root
CIST
Regional Root
Caution: Spanning Tree configuration should be performed only by personnel who are very
knowledgeable about Spanning Trees and the configuration of the Spanning Tree Algorithms.
Otherwise, the proper operation of the network could be at risk.