1-37
z
Enable Digest Snooping on Device A and Device B so that the three routers can communicate with
one another.
Figure 1-8
Digest Snooping configuration
Configuration procedure
1) Enable Digest Snooping on Device A.
# Enable Digest Snooping on GigabitEthernet 1/0/2.
<DeviceA> system-view
[DeviceA] interface gigabitethernet 1/0/2
[DeviceA-GigabitEthernet1/0/2] stp config-digest-snooping
[DeviceA-GigabitEthernet1/0/2] quit
# Enable global Digest Snooping.
[DeviceA] stp config-digest-snooping
2) Enable Digest Snooping on GigabitEthernet 1/0/1 of Device B (the same as above, omitted)
Configuring No Agreement Check
In RSTP and MSTP, two types of messages are used for rapid state transition on designated ports:
z
Proposal: sent by designated ports to request rapid transition
z
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. The differences between RSTP and MSTP
devices are:
z
For MSTP, the downstream device’s root port sends an agreement packet only after it receives an
agreement packet from the upstream device.
z
For RSTP, the down stream device sends an agreement packet regardless of whether an
agreement packet from the upstream device is received.
Figure 1-9
shows the rapid state transition mechanism on MSTP designated ports.
