Rstp/Mstp Definitions; Figure 2: Cisco R-Pvst Interoperability With Avaya - Avaya 8600 Engineering

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Figure 2: Cisco R-PVST Interoperability with Avaya

1.11 RSTP/MSTP Definitions

As per the IEEE 802.1s (MSTP) [integrated in IEEE 802.1Q-2005] and IEEE 802.1w (RSTP) [integrated
in IEEE 802.1D-2004] standards:
Boundary Port: A Bridge Port attaching an MST Bridge to a LAN that is not in the same region.
Common and Internal Spanning Tree (CIST): The single Spanning Tree calculated by STP and RSTP
together with the logical continuation of that connectivity through MST Bridges and regions, calculated by
MSTP to ensure that all LANs in the Bridged Local Area Network are simply and fully connected.
Common Spanning Tree (CST): The single Spanning Tree calculated by STP and RSTP, and by MSTP
to connect MST Regions.
Internal Spanning Tree (IST): An internal Spanning Tree that runs in a given MST Region. Within a MST
region, multiple Spanning Instances may be configured. Instance 0 within a region is known as the
Internal Spanning Tree (IST).
Multiple Spanning Tree (MST) Configuration Identifier: A name for revision level, and a summary of a
given allocation of VLANs to Spanning Trees.
NOTE - Each MST Bridge uses a single MST Configuration Table and Configuration Identifier.
MST Configuration Table: A configurable table that allocates each and every possible VLAN to the
Common Spanning Tree or a specific Multiple Spanning Tree Instance.
Multiple Spanning Tree Algorithm and Protocol (MSTP): The Multiple Spanning Tree Algorithm and
Protocol.
MST Bridge: A Bridge capable of supporting the CST, and one or more MSTIs and of selectively
mapping frames classified in any given VLAN to the CST or a given MSTI.
MST Region: A set of LANs and MST Bridges physically connected via Ports on those MST Bridges,
where each LAN's CIST Designated Bridge is an MST Bridge, and each Port is either the Designated
Port on one of the LANs, or else a non-Designated Port of an MST Bridge that is connected to one of the
LANs, whose MST Configuration Identifier (MCID) matches exactly the MCID of the Designated Bridge of
that LAN.
RSTP/MSTP Technical Configuration Guide
15
July 2010