Cisco SGE2000 Reference Guide - Page 169
Root Guard, Port State, Port Role, Path Cost, Priority, Designated Bridge ID
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Chapter SGE2000/SGE2000P Gigabit Ethernet Switch Reference Guide 10 optimizes the STP protocol convergence. STP convergence can take 30-60 seconds in large networks. • Root Guard - Prevents devices outside the network core from being assigned the spanning tree root. • 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 in Listening mode. The port cannot forward traffic nor can it learn MAC addresses. - Learning - Indicates that the port is in Learning mode. The port cannot forward traffic, however it can learn new MAC addresses. - Forwarding - Indicates that the port is in Forwarding mode. The port 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 LAG 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. • 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 being rerouted. • Priority - Priority value of the port. The priority value influences the port choice when a bridge has two ports connected in a loop. The priority value is between 0 -240. The priority value is provided in increments of 16. • Designated Bridge ID - Indicates the bridge priority and the MAC Address of the designated bridge. • Designated Port ID - Indicates the selected port's priority and interface. Chapter 10: Configuring Spanning Tree 161 Defining Interface Settings