Rapid Transition Configuration - Huawei Quidway S3900 Series Operation Manual

Operation Manual – MSTP
Quidway S3900 Series Ethernet Switches-Release 1510
Note:
The digest snooping feature is needed only when your S3900 series switch is
connected to partner's proprietary protocol-adopted switches.
To enable the digest snooping feature successfully, you must first enable it on all the
ports of your S3900 series switch that are connected to partner's proprietary
protocol-adopted switches and then enable it globally.
To enable the digest snooping feature, the interconnected switches must be
configured with exactly the same MST region-related configurations (including
region name, revision level, and VLAN-to-MSTI mapping).
The digest snooping feature must be enabled on all the ports of your S3900 switch
that are connected to partners' proprietary protocol-adopted switches in the same
MST region.
With the digest snooping feature is enabled, the VLAN-to-MSTI mapping cannot be
modified.
The digest snooping feature is not applicable on MST region edge ports.

1.7 Rapid Transition Configuration

1.7.1 Introduction
Designated ports on switches adopting RSTP or MSTP use the following two types of
packets to implement rapid transition:
Proposal packets: Packets sent by designated ports to request rapid transition
Agreement packets: Packets used to acknowledge rapid transition requests
Both RSTP and MSTP switches can perform rapid transition operation on a designated
port only when the port receives an agreement packet from the downstream switch.
The difference between RSTP and MSTP switches are:
An MSTP upstream switch sends agreement packets to the downstream switch;
and an MSTP downstream switch sends an agreement packet to the upstream
switch only after it receives an agreement packet from the upstream switch.
A RSTP upstream switch does not send agreement packets to the downstream
switch.
Figure 1-3 and Figure 1-4 illustrate the RSTP and MSTP rapid transition mechanisms.
Huawei Technologies Proprietary
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Chapter 1 MSTP Configuration