230 CHAPTER 23: MSTP CONFIGURATION
■ You need to enable this feature both globally and on associated ports to make
it take effect. It is recommended to enable the feature on all associated ports
first and then globally, making all configured ports take effect, and disable the
feature globally to disable it on all associated ports.
■ It is not recommended to enable Digest Snooping on the MST region edge port
to avoid loops.
■ It is recommended to enable Digest Snooping first and then MSTP. Do not
enable Digest Snooping when the network works well to avoid traffic
interruption.
Configuration Example Network requirements
■ Device A and Device B connect to a third-party’s router and all the routers are in
the same region.
■ Enable Digest Snooping on Device A and Device B so that the three routers can
communicate with one another.
Network diagram
Figure 58 Digest Snooping configuration
Configuration procedure
1 Enable Digest Snooping on Device A
# Enable Digest Snooping on GigabitEthernet1/0/1.
<DeviceA> system-view
[DeviceA] interface GigabitEthernet 1/0/1
[DeviceA-GigabitEthernet1/0/1] stp config-digest-snooping
# Enable global Digest Snooping.
[DeviceA-GigabitEthernet1/0/1] quit
[DeviceA] stp config-digest-snooping
2 Enable Digest Snooping on Device B (the same as above, omitted)
Configuring No
Agreement Check
Two types of messages are used for rapid state transition on designated RSTP and
MSTP ports:
■ Proposal: sent by designated ports to request rapid transition
■ Agreement: used to acknowledge rapid transition requests
Third-party switch
Root port
Designated port
Blocked port
GE1/0/1
GE1/0/1
GE1/0/2
GE1/0/1
GE1/0/2
GE1/0/2
Device A
Device B
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