H3C Technologies H3C S12500-X Series Switches - Manual (Page 102)

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[DeviceB-Ten-GigabitEthernet1/0/1] quit
[DeviceB] stp global config-digest-snooping
Configuring No Agreement Check
In RSTP and MSTP, the following types of messages are used for rapid state transition on designated
ports:
• Proposal—Sent by designated ports to request rapid transition
• Agreement—Used to acknowledge rapid transition requests
Both RSTP and MSTP devices can perform rapid transition on a designated port only when the port
receives an agreement packet from the downstream device. RSTP and MSTP devices have the following
differences:
• For MSTP, the root port of the downstream device sends an agreement packet only after it receives
an agreement packet from the upstream device.
• For RSTP, the downstream device sends an agreement packet regardless of whether an agreement
packet from the upstream device is received.
Figure 22 Rapid state transition of an MSTP designated port
Figure 23 Rapid state transition of an RSTP designated port
If the upstream device is a third-party device, the rapid state transition implementation might 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