H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 91)

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Figure 20 Rapid state transition of an MSTP designated port
Figure 21 shows rapid state transition of an RSTP designated port.
Figure 21 Rapid state transition of an RSTP designated port
If the upstream device is a third-party device, the rapid state transition implementation may be limited.
For example, when the upstream device uses a rapid transition mechanism similar to that of RSTP, and the
downstream device adopts MSTP and does not operate in RSTP mode, the root port on the downstream
device receives no agreement packet from the upstream device and sends no agreement packets to the
upstream device. As a result, the designated port of the upstream device fails to transit rapidly and can
only change to the forwarding state after a period twice the Forward Delay.
You can enable the No Agreement Check feature on the port of the downstream device to enable the
designated port of the upstream device to transit its state rapidly.
Configuration prerequisites
Before you configure the No Agreement Check function, complete the following tasks:
• Connect a device to a third-party upstream device supporting spanning tree protocols via a
point-to-point link.
• Configure the same region name, revision level, and VLAN-to-instance mappings on the two
devices, assigning them to the same region.
Root port Designated port
Upstream device Downstream device
(1) Proposal for rapid transition
(3) Agreement
The root port blocks non-edge
ports.
The root port changes to the
forwarding state and sends an
Agreement to the upstream
device.
(2) Agreement
The designated port
changes to the
forwarding state.
Root port Designated port
Upstream device Downstream device
(1) Proposal for rapid transition
(2) Agreement
The root port blocks non-edge
ports, changes to the forwarding
state, and sends an Agreement to
the upstream device.
The designated
port changes to the
forwarding state.