Multiple Spanning Tree Protocol; Mstp Region; Common Internal Spanning Tree - Lenovo RackSwitch G8264 Application Manual

Multiple Spanning Tree Protocol

MSTP Region

Common Internal Spanning Tree

204
G8264 Application Guide for ENOS 8.4
Multiple Spanning Tree Protocol (MSTP) extends Rapid Spanning Tree Protocol
(RSTP), allowing multiple Spanning Tree Groups (STGs) which may each include
multiple VLANs. MSTP was originally defined in IEEE 802.1s (2002) and was later
included in IEEE 802.1Q (2003).
In MSTP mode, the G8264 supports up to 32 instances of Spanning Tree,
corresponding to STGs 1‐32, with each STG acting as an independent,
simultaneous instance of RSTP.
MSTP allows frames assigned to different VLANs to follow separate paths, with
each path based on an independent Spanning Tree instance. This approach
provides multiple forwarding paths for data traffic, thereby enabling
load‐balancing, and reducing the number of Spanning Tree instances required to
support a large number of VLANs.
Due to Spanning Tree's sequence of discarding, learning, and forwarding, lengthy
delays may occur while paths are being resolved. Ports defined as edge/portfast
ports ("Port Type and Link Type" on page
Learning states, and enter directly into the Forwarding state.
Note: In MSTP mode, Spanning Tree for the management ports is turned off by
default.
A group of interconnected bridges that share the same attributes is called an MST
region. Each bridge within the region must share the following attributes:
 Alphanumeric name
Revision number

 VLAN‐to STG mapping scheme
MSTP provides rapid re‐configuration, scalability and control due to the support
of regions, and multiple Spanning‐Tree instances support within each region.
The Common Internal Spanning Tree (CIST) or MST0 provides a common form of
Spanning Tree Protocol, with one Spanning‐Tree instance that can be used
throughout the MSTP region. CIST allows the switch to interoperate with legacy
equipment, including devices that run IEEE 802.1D (1998) STP.
CIST allows the MSTP region to act as a virtual bridge to other bridges outside of
the region, and provides a single Spanning‐Tree instance to interact with them.
CIST port configuration includes Hello time, path‐cost, and interface priority.
These parameters do not affect Spanning Tree Groups 1‐32. They apply only when
the CIST is used.
208) bypass the Discarding and