3Com Switch 8800 Advanced Software V5 Configuration Guide

Configuring No Agreement Check 129
Figure 33 Rapid state transition mechanism on the MSTP designated port
Figure 34 Rapid state transition mechanism on the RSTP designated port
If the upstream device comes from another vendor, the rapid state transition
implementation may be limited. For example, when the upstream device adopts
RSTP, the downstream device adopts MSTP and does not support RSTP mode, the
root port on the downstream device receives no agreement packet from the
upstream device and thus sends no agreement packets to the upstream device. As
a result, the designated port of the upstream switch fails to transit rapidly and can
only change to the Forwarding state after a period twice the Forward Delay.
In this case, you can enable the No Agreement Check feature on the downstream
device’s port to perform rapid state transition.
Configuration
Prerequisites
■ A device is the upstream one that is connected to another vendor’s MSTP
supported device via a point-to-point link.
■ Configure the same region name, revision level and VLAN-to-instance
mappings on the two devices, making them in the same region.
Configuration Procedure Following these steps to configure No Agreement Check:
Upstream switch
Downstream switch
Proposal for rapid transition
Agreement
A
g
r
e
e
m
e
n
t
Root port
Designated port
Root port changes to forwarding
to upstream switch
Designated port
changes to
forwarding state
Root port blocks other
non-edge ports
Designated port
changes to
forwarding state
Upstream switch
Downstream switch
Proposal for rapid transition
Root port
Designated port
Root port blocks other non -
edge ports, changes to
forwarding state and sends
agreement packet to upstream
switch
A
g
r
e
e
m
e
n
t
To do... Use the command... Remarks
Enter system view system-view -