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Spanning Tree Algorithm Configuration
3-147
3
CLI – This example shows the STA attributes for port 5.
Configuring Interface Settings
You can configure RSTP and MSTP attributes for specific interfaces, including port
priority, path cost, link type, and edge port. You may use a different priority or path
cost for ports of the same media type to indicate the preferred path, link type to
indicate a point-to-point connection or shared-media connection, and edge port to
indicate if the attached device can support fast forwarding. (References to “ports” in
this section means “interfaces,” which includes both ports and trunks.)
Command Attributes
The following attributes are read-only and cannot be changed:
• STA State – Displays current state of this port within the Spanning Tree.
(See Displaying Interface Settings on page 3-144 for additional information.)
- Discarding - Port receives STA configuration messages, but does not forward
packets.
- Learning - Port has transmitted configuration messages for an interval set by
the Forward Delay parameter without receiving contradictory information. Port
address table is cleared, and the port begins learning addresses.
- Forwarding - Port forwards packets, and continues learning addresses.
• Trunk – Indicates if a port is a member of a trunk. (STA Port Configuration only)
The following interface attributes can be configured:
• Spanning Tree – Enables/disables STA on this interface. (Default: Enabled).
• Priority – Defines the priority used for this port in the Spanning Tree Protocol. If
the path cost for all ports on a switch are the same, the port with the highest priority
(i.e., lowest value) will be configured as an active link in the Spanning Tree. This
makes a port with higher priority less likely to be blocked if the Spanning Tree
Console#show spanning-tree ethernet 1/5 4-235
Eth 1/ 5 information
--------------------------------------------------------------
Admin status: enabled
Role: disable
State: discarding
Path cost: 10000
Priority: 128
Designated cost: 0
Designated port : 128.5
Designated root: 32768.0012CF0B0D00
Designated bridge: 32768.0012CF0B0D00
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
Console#