Configuring No Agreement Check - 3Com MSR 50 Series Configuration Manual

Configuring No
Agreement Check
Two types of packet are used for rapid state transition on designated RSTP and
MSTP ports:
Proposal: Packets sent by designated ports to request rapid transition
■
Agreement: Packets used to acknowledge rapid transition requests
■
Both RSTP and MSTP devices can perform rapid transition operation 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 down stream device sends an agreement packet regardless of
■
whether an agreement packet from the upstream device is received.
Figure 133 and Figure 134
and RSTP designated ports.
Figure 133 Rapid state transition mechanism on the MSTP designated port
Upstream switch
Designated port
changes to
forwarding state
Figure 134 Rapid state transition mechanism on the RSTP designated port
Upstream switch
Designated port
changes to
forwarding state
If the upstream device comes from another vendor, the rapid state transition
implementation may be limited. For example, when the upstream device adopts
RSTP, the downstream device adopts MSTP and does not support RSTP mode, the
root port on the downstream device receives no agreement packet from the

Configuring No Agreement Check

show the rapid state transition mechanism on MSTP
Downstream switch
Proposal for rapid transition
Agreement
Proposal for rapid transition
Root port blocks other
non-edge ports
Root port changes to forwarding
to upstream switch
Root port
Designated port
Downstream switch
Root port blocks other non -
edge ports, changes to
forwarding state and sends
agreement packet to upstream
switch
Root port
Designated port
477