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Spanning Tree Algorithm Configuration
3-119
3
Note: The current root port and current root cost display as zero when this device is not
connected to the network.
Configuring Global Settings
Global settings apply to the entire switch.
Command Usage
• Spanning Tree Protocol
12
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
12
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 (i.e., STP 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.
Transmission limit: 3
Path Cost Method: long
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Eth 1/ 1 information
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Admin status: enabled
Role: disable
State: discarding
External admin path cost: 10000
Internal admin cost: 10000
External oper path cost: 10000
Internal oper path cost: 10000
Priority: 128
Designated cost: 300000
Designated port: 128.1
Designated root: 32768.0000E8AAAA00
Designated bridge: 32768.0030F1D473A0
Fast forwarding: disabled
Forward transitions: 0
Admin edge port: disabled
Oper edge port: disabled
Admin Link type: auto
Oper Link type: point-to-point
Spanning Tree Status: enabled
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12. STP and RSTP BPDUs are transmitted as untagged frames, and will cross any VLAN
boundaries.