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Spanning Tree Commands
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an STA-compliant switch, bridge or router) in your network to ensure that only
one route exists between any two stations on the network, and provide backup
links which automatically take over when a primary link goes down.
Example
This example shows how to enable the Spanning Tree Algorithm for the switch:
spanning-tree mode
This command selects the spanning tree mode for this switch. Use the no form to
restore the default.
Note:
MSTP is not supported in the current software.
Syntax
spanning-tree mode {stp | rstp
| mstp}
no spanning-tree mode
• stp - Spanning Tree Protocol (IEEE 802.1D)
• rstp - Rapid Spanning Tree Protocol (IEEE 802.1w)
• mstp - Multiple Spanning Tree (IEEE 802.1s)
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.
Console(config)#spanning-tree
Console(config)#