Configuring Rapid Transition; Introduction - 3Com WX3000 Series Operation Manual

When the digest snooping feature is enabled on a port, the port state turns to the discarding state.
That is, the port will not send BPDU packets. The port is not involved in the STP calculation until it
receives BPDU packets from the peer port.
The digest snooping feature is needed only when your device is connected to a device of another
vendor adopting proprietary spanning tree protocols.
To enable the digest snooping feature successfully, you must first enable it on all the ports of your
device that are connected to a device of another vendor adopting proprietary spanning tree
protocols and then enable it globally.
To enable the digest snooping feature, the interconnected devices and the devices of another
vendor adopting proprietary spanning tree protocols must be configured with exactly the same
MST region-related configurations (including region name, revision level, and VLAN-to-MSTI
mapping).
The digest snooping feature must be enabled on all the device ports that connect to the devices of
other vendors adopting proprietary spanning tree protocols in the same MST region.
When the digest snooping feature is enabled globally, the VLAN-to-MSTI mapping table cannot be
modified.
The digest snooping feature is not applicable to boundary ports in an MST region.
The digest snooping feature is not applicable to edge ports in an MST region.

Configuring Rapid Transition

Introduction

Designated ports of RSTP-enabled or MSTP-enabled devices use the following two types of packets to
implement rapid transition:
Proposal packets: Packets sent by designated ports to request rapid transition
Agreement packets: Packets used to acknowledge rapid transition requests
Both RSTP and MSTP specify that the upstream device can perform rapid transition operation on the
designated port only when the port receives an agreement packet from the downstream device. The
difference between RSTP and MSTP are:
For MSTP, the upstream device sends agreement packets to the downstream device; and the
downstream device sends agreement packets to the upstream device only after it receives
agreement packets from the upstream device.
For RSTP, the upstream device does not send agreement packets to the downstream device.
Figure 1-6 and Figure 1-7
MSTP.
illustrate the rapid transition mechanisms on designated ports in RSTP and
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