Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 487)

Spanning Tree Introduction: STP, RSTP, and MSTP
Software Reference for x310 Series Switches
C613-50046-01 REV A AlliedWare Plus TM Operating System - Version 5.4.4C 18.19
Configuring MSTP
By default, RSTP is enabled with default settings on all switch ports. To configure MSTP, see
the configuration procedure in
Table 18-9 .
To configure other modes, see “Configuring RSTP” on page 18.9 or “Configuring STP”
on page 18.6 .
For detailed configuration examples, see the How To Note How To Configure Basic
Switching Functionality, available from website at
http://www.alliedtelesis.com .
Configuration
guidelines for
MSTP
■ Switches must have the same MST configuration identification elements (region
name, revision level and VLAN to MSTI mapping) to be in the same MST region. When
configuring multiple MST regions for MSTP, MSTIs are locally significant within an MST
region. MSTIs will not span from one region to another region.
■ Common and Internal Spanning Tree (CIST) is the default spanning tree instance for
MSTP. This means that all VLANs that are not explicitly configured into another MSTI
are members of the CIST.
■ The software supports a single instance of the MSTP Algorithm consisting of the CIST
and up to 15 MSTIs.
■ A VLAN can only be mapped to one MSTI or to the CIST. One VLAN mapped to
multiple spanning trees is not allowed. All the VLANs are mapped to the CIST by
default. Once a VLAN is mapped to a specified MSTI, it is removed from the CIST.
■ An MSTI is locally significant within an MST region. An MSTI cannot span across
multiple MST regions. The CIST is the spanning tree instance for connecting different
MST regions and single spanning tree entities, such as RSTP and STP switches.
■ MSTP is compatible with RSTP and STP. An MST region appears as a virtual bridge
connecting to single spanning tree entities.
■ To avoid unnecessary STP processing, a port that attaches to a LAN that is known to
have no other bridges/switches attached can be configured as an edge port.
Before configuring
MSTP
Before configuring MSTP, configure VLANs and associate them with switch ports
(
Chapter 16, VLAN Introduction and Chapter 17, VLAN Commands ), and determine for
your network:
■ which MSTP regions, revision level and instances are required
■ which VLANs and switch ports will belong to which MSTIs,
■ which devices you want to be root bridges for each MSTI
Table 18-9: Configuration procedure for MSTP
Command Description
awplus#
configure terminal Enter Global Configuration mode.
awplus(config)#
spanning-tree mode mstp By default, the device is in RSTP mode. Change to MSTP
mode.
awplus(config)#
spanning-tree enable By default, spanning tree is enabled on all switch ports. If
it has been disabled, enable it for MSTP.