Configuring Spanning Tree
Configuring Classic Spanning Tree
Page 137
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Port Fast
— Indicates if Fast Link is enabled on the port. If Fast Link mode is enabled for a port, the
Port
State
is automatically placed in the
Forwarding
state
when the port link is up. Fast Link optimizes the STP
protocol convergence. STP convergence can take 30-60 seconds in large networks. The possible field values
are:
–
Enable
— Enables Port Fast.
–
Disable
— Disables Port Fast.
–
Auto
— Indicates that Port Fast mode is enabled a few seconds after the interface becomes active.
•
Root Guard
— Prevents devices outside the network core from being assigned the spanning tree root. The
possible field values are:
–
Enable
— Enables Root Guard.
–
Disable
— Disables Root Guard.
•
BPDU Guard
— Protects the network from invalid configurations by shutting down an interface when a
BPDU message is received. The possible field values are:
–
Enable
— Enables BPDU Guard.
–
Disable
— Disables BPDU Guard.
•
Port State
— Displays the current STP state of a port. If enabled, the port state determines what forwarding
action is taken on traffic. Possible port states are:
–
Disabled
— Indicates that STP is currently disabled on the port. The port forwards traffic while learning
MAC addresses.
–
Blocking
— Indicates that the port is currently blocked and cannot forward traffic or learn MAC
addresses. Blocking is displayed when Classic STP is enabled.
–
Listening
— Indicates that the port is currently in the listening mode. The interface cannot forward traffic
nor can it learn MAC addresses.
–
Learning
— Indicates the port is currently in the learning mode. The interface cannot forward traffic;
however, it can learn new MAC addresses.
–
Forwarding
— Indicates the port is currently in the forwarding mode. The port can forward traffic and
learn new MAC addresses. The interface can forward traffic and learn new MAC addresses.
•
Port Role
— Displays the port role assigned by the STP algorithm to provide to STP paths. The possible field
values are:
–
Root
— Provides the lowest cost path to forward packets to the root switch.
–
Designated
— The port or trunk through which the designated switch is attached to the LAN.
–
Alternate
— Provides an alternate path to the root switch from the root interface.
–
Backup
— Provides a backup path to the designated port path toward the Spanning Tree leaves. Backup
ports occur only when two ports are connected in a loop by a point-to-point link, or when a LAN has two
or more connections connected to a shared segment.
–
Disabled
— The port is not participating in the Spanning Tree.
•
Speed
— Indicates the speed at which the port is operating.
•
Path Cost
— Indicates the port contribution to the root path cost. The path cost is adjusted to a higher or
lower value, and is used to forward traffic when a path is rerouted.
•
Priority
— Indicates the priority value of the port connected to the selected port. A lower priority increases
the probability of connecting to a root port. The priority value is between 0-240. The priority value is
determined in increments of 16.
•
Designated Bridge ID
— Indicates the bridge priority and the MAC Address of the designated bridge.
•
Designated Port ID
— Indicates the designated port priority and interface.
•
Designated Cost
— Indicates the cost of the port participating in the STP topology. Ports with a lower cost
are less likely to be blocked if STP detects loops.
