Transitioning From Stp To Rstp - HP ProCurve Series 4100GL Management And Configuration Manual

802.1w Rapid Spanning Tree Protocol (RSTP) and 802.1d Spanning Tree Protocol (STP)
Configuring Rapid Reconfiguration Spanning Tree (RSTP)
N o t e
14-8
As indicated in the manual, the spanning tree protocol is used to ensure that
only one active path at a time exists between any two end nodes in the network
in which your switch is installed. Multiple paths cause a loop in the network
over which broadcast and multicast messages are repeated continuously,
which floods the network with traffic creating a broadcast storm.
In networks where there is more than one physical path between any two
nodes, enabling spanning tree ensures a single active path between two such
nodes by selecting the one most efficient path and blocking the other redun­
dant paths. If a switch or bridge in the path becomes disabled, spanning tree
activates the necessary blocked segments to create the next most efficient
path.

Transitioning from STP to RSTP

IEEE 802.1w RSTP is designed to be compatible with IEEE 802.1D STP. Even
if all the other devices in your network are using STP, you can enable RSTP
on your switch, and even using the default configuration values, your switch
will interoperate effectively with the STP devices. If any of the switch ports
are connected to switches or bridges on your network that do not support
RSTP, RSTP can still be used on this switch. RSTP automatically detects when
the switch ports are connected to non-RSTP devices in the spanning tree and
communicates with those devices using 802.1D STP BPDU packets.
Because RSTP is so much more efficient at establishing the network path, it
is highly recommended that all your network devices be updated to support
RSTP. RSTP offers convergence times of less than one second under optimal
circumstances. To make the best use of RSTP and achieve the fastest possible
convergence times, though, there are some changes that you should make to
the RSTP default configuration. See "Optimizing the RSTP Configuration"
below, for more information on these changes.
Under some circumstances, it is possible for the rapid state transitions
employed by RSTP to result in an increase in the rates of frame duplication
and misordering in the switched LAN. In order to allow RSTP switches to
support applications and protocols that may be sensitive to frame duplication
and misordering, setting the Force Protocol Version parameter to STP-com -
patible allows RSTP to be operated with the rapid transitions disabled. The
value of this parameter applies to all ports on the switch. See information on
Force Version on page 14-12.
As indicated above, one of the benefits of RSTP is the implementation of a
larger range of port path costs, which accommodates higher network speeds.
New default values have also been implemented for the path costs associated