CST Port Configuration
Use the CST Port page to view and configure the Common Spanning Tree (CST) settings for each
interface on the device. To configure CST settings for an interface and to view additional information
about the interface's role in the CST topology, select the interface to view or configure and click
Edit
.
To display the Spanning Tree CST Port Configuration/Status page, click
Switching
>
Spanning Tree
>
CST Port
in the navigation menu.
Table 231: Spanning Tree CST Port Fields
Field
Description
Interface
associated with the rest of the data in the row. When
configuring CST settings for an interface, this field identifies the interface being
configured.
Port Role
The role of the port within the CST, which is one of the following:
•
Root – A port on the non-root bridge that has the least-cost path to the root
bridge.
•
Designated – A port that has the least-cost path to the root bridge on its
segment.
•
Alternate – A blocked port that has an alternate path to the root bridge.
•
Backup – A blocked port that has a redundant path to the same network
segment as another port on the bridge.
•
Master – The port on a bridge within an MST instance that links the MST
instance to other
regions.
•
Disabled – The port is administratively disabled and is not part of the
spanning tree.
Port Forwarding State
•
Blocking – The port discards user traffic and receives, but does not send,
BPDUs. During the election process, all ports are in the blocking state. The
port is blocked to prevent network loops.
•
Listening – The port sends and receives BPDUs and evaluates information to
provide a loop-free topology. This state occurs during network convergence
and is the first state in transitioning to the forwarding state.
•
Learning – The port learns the MAC addresses of frames it receives and
begins to populate the MAC address table. This state occurs during network
convergence and is the second state in transitioning to the forwarding state.
•
Forwarding – The port sends and receives user traffic.
•
Disabled – The port is administratively disabled and is not part of the
spanning tree.
Port Priority
The priority for the port within the CST. This value is used in determining which
port on a switch becomes the root port when two ports have the same least-cost
path to the root. The port with the lower priority value becomes the root port. If
the priority values are the same, the port with the lower interface index becomes
the root port.
Port Path Cost
The path cost from the port to the root bridge.
Description
A user-configured description of the port. After you select an interface and click
Edit
, a window opens and allows you to edit the CST port settings and view
additional CST information for the interface. The following information describes
the additional fields available in the Edit CST Port Entry window.
Configuring Switching Information
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