Default Setting
rstp
Command Mode
Global Configuration
Command Usage
• Spanning Tree Protocol
Uses RSTP for the internal state machine, but sends only 802.1D BPDUs.
- This creates one spanning tree instan ce for the en tire netwo rk. If m ultiple
VLANs are implemented on a network, the path between specif ic VLAN
members may be inadvertently disabled to prevent network loops, thus
isolating group members. When operating multiple VLANs, we recommend
selecting the MSTP option.
• Rapid Spanning Tree Protoco l
RSTP supports connections to either STP or RSTP nodes by monitoring
the incoming protocol messages and dynamically adjusting the type of
protocol messages the RSTP node transmits, as described below:
- STP Mode – If the switch receives an 802.1D BPDU after a port’s migration
delay timer expires, the switch assumes it is connected to an 802.1D bridge
and starts using only 802.1D BPDUs.
- RSTP Mode – If RSTP is using 802.1D BPDU s on a port an d receiv es an
RSTP BPDU after the migration delay expires, RSTP restarts the migration
delay timer and begins using RSTP BPDUs on that po rt.
• Multiple Spanning Tree Protocol
- To allow multiple spanning trees t o operate over the network, you must
configure a related set of bridges with the same MSTP configuration ,
allowing them to participate in a specific set of s panning tr ee instan ces.
- A spanning tree instance can exist only on brid ges that ha ve compatib le
VLAN instance assignments.
- Be careful when switching between spanning tree modes. Changing modes
stops all spanning-tree instances for the previou s mode and resta rts the
system in the new mode, temporarily disrupting user traffic.
Example
The following example configures the switch to use Rapid Spanning Tree:
Console(config)#spanning-tree mode rstp
Console(config)#
33-3spanning-tree mode
33