Allied Telesis AT-S94 - Manual (Page 139)

Configuring Spanning Tree
Configuring Classic Spanning Tree
Page 139
• 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.