Blade ICE G8000 - Manual (Page 80)

RackSwitch G8000 Application Guide
80 „ Chapter 5: Spanning Tree BMD00041, November 2008
Rapid Spanning Tree Protocol
Rapid Spanning Tree Protocol (RSTP) provides rapid convergence of the spanning tree and
provides for fast re-configuration critical for networks carrying delay-sensitive traffic such as
voice and video. RSTP significantly reduces the time to reconfigure the active topology of the
network when changes occur to the physical topology or its configuration parameters. RSTP
reduces the bridged-LAN topology to a single Spanning Tree.
RSTP parameters are configured in Spanning Tree Group 1. STP Groups 2-128 do not apply to
RSTP. There are new STP parameters to support RSTP, and some values to existing parameters
are different.
RSTP is compatible with devices that run 802.1D (1998) Spanning Tree Protocol. If the switch
detects 802.1D (1998) BPDUs, it responds with 802.1D (1998)-compatible data units. RSTP is
not compatible with Per VLAN Spanning Tree (PVST+) protocol.
Port state changes
The port state controls the forwarding and learning processes of Spanning Tree. In RSTP, the
port state has been consolidated to the following: discarding, learning, and forwarding.
Table 3
compares the port states between 802.1D (1998) Spanning Tree and 802.1D (2004) Rapid
Spanning Tree.
Table 3 RSTP vs. STP Port states
Operational status STP Port State RSTP Port State
Enabled Blocking Discarding
Enabled Listening Discarding
Enabled Learning Learning
Enabled Forwarding Forwarding
Disabled Disabled Discarding