Figure 7-10
Enhanced P/A mechanism
Upstream
device
Downstream
device
Sends a proposal so
that the port can
rapidly enter the
Forwarding state
Sends an agreement
Sends an agreement
The root port blocks
all the other non-
edge ports
The root port
enters the
Forwarding state
The designated
port enters the
Forwarding state
root port
designated port
, in MSTP, the P/A mechanism works as follows:
1.
The upstream device sends a proposal to the downstream device, indicating that the
port connecting to the downstream device wants to enter the Forwarding state as soon
as possible. After receiving this BPDU, the downstream device sets its port connecting
to the upstream device to the root port, and blocks all non-edge ports.
2.
The upstream device continues to send an agreement. After receiving this BPDU, the
root port enters the Forwarding state.
3.
The downstream device replies with an agreement. After receiving this BPDU, the
upstream device sets its port connecting to the downstream device to the designated
port, and the port enters the Forwarding state.
By default, Huawei datacom devices use the fast transition mechanism in enhanced mode. To
enable a Huawei datacom device to communicate with a third-party device that use the fast
transition mechanism in common mode, configure the Proposal/Agreement mechanism on the
Huawei datacom device so that the Huawei datacom device works in common mode.
7.3 Application Environment
This section describes the applicable environment of MSTP.
Huawei AR530&AR550 Series Industrial Switch Routers
Configuration Guide - Ethernet Switching
7 MSTP Configuration
Issue 01 (2014-11-30)
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