IBM RackSwitch G8000, Application Manual

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RackSwitch G8000: Application Guide
Rapid Spanning Tree Protocol
RSTP provides rapid convergence of the Spanning Tree and provides the 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 was originally defined in IEEE 802.1w (2001) and was later incorporated into
IEEE 802.1D (2004), superseding the original STP standard.
RSTP parameters apply only to Spanning Tree Group (STG) 1. The PVRST mode
STGs 2-128 are not used when the switch is placed in RSTP mode.
RSTP is compatible with devices that run IEEE 802.1D (1998) Spanning Tree
Protocol. If the switch detects IEEE 802.1D (1998) BPDUs, it responds with IEEE
802.1D (1998)-compatible data units. RSTP is not compatible with Per-VLAN Rapid
Spanning Tree (PVRST) protocol.
Port States
RSTP port state controls are the same as for PVRST:
discarding
,
learning
,
and
forwarding
.
Due to the sequence involved in these STP states, considerable delays may occur
while paths are being resolved. To mitigate delays, ports defined as edge ports
( “Port Type and Link Type” on page 129 ) may bypass the
discarding
and
learning
states, and enter directly into the
forwarding
state.
RSTP Configuration Guidelines
This section provides important information about configuring RSTP. When RSTP is
turned on, the following occurs:
•
STP parameters apply only to STG 1.
• Only STG 1 is available. All other STGs are turned off.
• All VLANs are moved to STG 1.
RSTP Configuration Example
This section provides steps to configure RSTP.
1. Configure port and VLAN membership on the switch.
2. Set the Spanning Tree mode to Rapid Spanning Tree.
3. Configure STP Group 1 parameters.
RS G8000(config)#
spanning-tree mode rstp
RS G8000(config)#
spanning-tree stp 1 enable
RS G8000(config)#
spanning-tree stp 1 vlan 2