HP A6600 Configuration Manual page 78

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:
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 20 shows the rapid state transition mechanism on MSTP designated ports.
Figure 20 Rapid state transition of an MSTP designated port
Figure 21 shows rapid state transition of an RSTP designated port.
Figure 21 Rapid state transition of an RSTP designated port
If the upstream device is a third-party device, the rapid state transition implementation may 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 work in RSTP mode, the root port on the downstream
device receives no agreement packet from the upstream device and thus sends no agreement packets to
the upstream device. As a result, the designated port of the upstream device fails to transit rapidly and
can only change to the forwarding state after a period twice the forward delay.
In this case, enable the no agreement check feature on the downstream device's port to enable the
designated port of the upstream device to transit its state rapidly.
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