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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 instance for the entire network. If multiple
VLANs are implemented on a network, the path between specific 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 Protocol
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 BPDUs on a port and receives an
RSTP BPDU after the migration delay expires, RSTP restarts the migration
delay timer and begins using RSTP BPDUs on that port.
• Multiple Spanning Tree Protocol
- To allow multiple spanning trees to 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 spanning tree instances.
- A spanning tree instance can exist only on bridges that have compatible
VLAN instance assignments.
- Be careful when switching between spanning tree modes. Changing modes
stops all spanning-tree instances for the previous mode and restarts 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)#
33-3
spanning-tree mode
33