Dell 6.2 Chapte r 26

DellPowerConnect W- Series ArubaOS 6.2 | User Guide RSTP | 485
Chapte r 26
RSTP
Dell’si mplementationo f Rapid Spanning Tree Protocol (RSTP) is as speci fied in 802.1w with backward
compatibility to legacy Spanning Tree (STP) 802.1D. RSTP t akes advantageof po int-to-point links and provides
rapid convergenceof t he spanningtree. RSTP is enabled by default on all Dell controllers.
Topics in this chapter include:
l"UnderstandingRSTP Migration and Interoperability" on page 48 5
l"Workingwith R apid Convergence"on page 485
l"ConfiguringRSTP" on page 48 7
l"TroubleshootingRSTP" on page 488
Understanding RS TP Migration and Interoperability
ArubaOSsupports RSTP on the following interfaces:
lFastEthernet IEEE 802.3—fastethernet
lGigabitethernet IEEE 802.3—gigabitethernet
lPort ChannelI D—port-channel
Working with Rapid Conv ergence
Since RSTP is backward compatiblewi th STP,i t is possible to configurebridges RSTP (and STP) in the same
network.However, such mixed networks may not always provide rapid convergence. RSTP provides rapid convergence
wheni nterfacesare configured as either:
lEdge ports—Theseare the interfaces/ports connected to hosts. These interfaces are immediately moved to the
forwardingstate. In this mode an interface forwards frames by default until it receives a BPDU (Bridge Protocol
Data Units) indicating that it should behaveotherwise; it does not go through the Listening andLearning states.
lPoint-to-Point links—These are the interfaces/ports connected directly to neighboring bridges over a point-to-
point link. RSTP negotiates with the neighbor bridgefor rapid convergence/transition only when the link is point-
to-point.
Table1 45 compares the port states between STP and RSTP.
STP (802.1d)
Port State
RSTP(8 02.1w)
Port State
Disabled Discarding
Blocking Discarding
Table14 5: PortState C omparison