H3C Technologies H3C S12500 Series Switches - Manual (Page 103)

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[DeviceA-GigabitEthernet4/0/1] quit
[DeviceA] stp config-digest-snooping
# Enable Digest Snooping on GigabitEthernet 4/0/1 of Device B and enable global Digest Snooping
on Device B.
system-view
[DeviceB] interface gigabitethernet 4/0/1
[DeviceB-GigabitEthernet4/0/1] stp config-digest-snooping
[DeviceB-GigabitEthernet4/0/1] quit
[DeviceB] stp 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 downstream device's root port 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 25 shows the rapid state transition mechanism on MSTP designated ports.
Figure 25 Rapid state transition of an MSTP designated port
Figure 26 shows rapid state transition of an RSTP designated port.
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.