Fast Reconfiguration - Hirschmann RS20 User Manual

Spanning Tree
Based on this information, the bridges participating in RSTP are able to
determine port roles themselves and define the port states of their own ports.
5.6.4

Fast reconfiguration

Why can RSTP react faster than STP to an interruption of the root path?
 Introduction of edge-ports:
During a reconfiguration, RSTP switches an edge port into the
transmission mode after three seconds and then waits for the "Hello Time"
(see table 13)
connected.
When the user determines that a terminal device is connected at this port
and will remain connected, he can switch off RSTP at this port. Thus no
waiting times occur at this port in the case of a reconfiguration.

Introduction of alternate ports:
As the port roles are already distributed in normal operation, a bridge can
immediately switch from the root port to the alternative port after the
connection to the root bridge is lost.
 Communication with neighboring bridges (point-to-point connections):
Decentralized, direct communication between neighboring bridges
enables reaction without wait periods to status changes in the spanning
tree topology.
 Address table:
With STP, the age of the entries in the FDB determines the updating of
communication. RSTP immediately deletes the entries in those ports
affected by a reconfiguration.

Reaction to events:
Without having to adhere to any time specifications, RSTP immediately
reacts to events such as connection interruptions, connection
reinstatements, etc.
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to elapse, to be sure that no bridge sending BPDUs is
5.6 The Rapid Spanning Tree
UM Redundancy Configuration L2E
Release 7.1 12/2011
Protocol