Multiple Spanning Tree Protocol (Mstp) - Allied Telesis SwitchBlade x908 Series Software Reference Manual

Spanning Tree Introduction: STP, RSTP, and MSTP
Multiple Spanning Tree Protocol
(MSTP)
Conceptually, MSTP views the total bridged network as one that comprises a number of
Multiple Spanning Tree Regions (MSTRs), where each region can contain up to 64 spanning trees
that operate locally, called Multiple Spanning Tree Instances (MSTIs). (This device supports up to
15 MSTIs.) The regions are linked by the Common Internal Spanning Tree (CIST). MSTP uses
BPDUs to exchange information between devices, and prevents loops for each MSTI and for
the CIST by selecting active and blocked paths, by the process described in
If multiple links are aggregated together into dynamic (LACP) or static channel groups, the
spanning tree application is notified and considers the links as a single logical path.
Advantage of MSTP is similar to RSTP, in that it provides loop resolution and rapid convergence. But it also
MSTP over RSTP has the significant extra advantage of making it possible to have different forwarding paths for
different MST instances. This enables load balancing of network traffic across redundant links, so
that all the links in a network can be used by at least one MSTI, and no link is left completely
idle.
18.10
Software Reference for SwitchBlade® x908, x900 and x600 Series Switches
TM
AlliedWare Plus Operating System - Software Version 5.3.1
Table 18-1.
C613-50007-01 REV B