Configuration Prerequisites; Configuration Procedure - H3C S5120-SI Series Operation Manual

Figure 1-9 Rapid state transition of an MSTP designated port
Figure 1-10 shows rapid state transition of an RSTP designated port.
Figure 1-10 Rapid state transition of an RSTP designated port
Upstream device
Designated port
changes to
forwarding state
If the upstream device comes from another vendor, 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 work in 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 device 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
enable the designated port of the upstream device to transit its state rapidly.

Configuration Prerequisites

A device is connected to an upstream device supporting MSTP via a point-to-point link.
Configure the same region name, revision level and VLAN-to-MSTI mappings on the two devices,
thus assigning them to the same region.

Configuration Procedure

Follow these steps to configure No Agreement Check:
Proposal for rapid transition
1-37
Downstream device
Root port blocks other non-
edge ports, changes to
forwarding state and sends
Agreement to upstream device
Root port
Designated port