Cisco Systems N3KC3064TFAL3 Specifying the Link Type, Restarting the Protocol, Procedure, Purpose

Configuring Multiple Spanning Tree

Specifying the Link Type

This example shows how to prevent the specified interfaces from automatically interoperating with a connecting switch that is not running MST:

switch# configure terminal switch(config)# interface ethernet 1/4

switch(config-if)#spanning-tree mst simulate pvst disable

Specifying the Link Type

Rapid connectivity (802.1w standard) is established only on point-to-point links. By default, the link type is controlled from the duplex mode of the interface. A full-duplex port is considered to have a point-to-point connection; a half-duplex port is considered to have a shared connection.

If you have a half-duplex link physically connected point-to-point to a single port on a remote switch, you can override the default setting on the link type and enable rapid transitions.

If you set the link to shared, STP reverts to 802.1D.

Procedure

Command or Action

Step 1 switch# configure terminal

Step 2 switch(config)# interface type slot/port

Step 3 switch(config-if)# spanning-treelink-type{auto point-to-point shared}

Purpose

Enters configuration mode.

Specifies the interface to configure, and enters interface configuration mode.

Configures the link type to be either point to point or shared. The system reads the default value from the switch connection. Half-duplex links are shared and full-duplex links are point to point. If the link type is shared, the STP reverts to 802.1D. The default is auto, which sets the link type based on the duplex setting of the interface.

This example shows how to configure the link type as point to point:

switch# configure terminal

switch (config)# interface ethernet 1/4 switch(config-if)# spanning-treelink-typepoint-to-point

Restarting the Protocol

An MST bridge can detect that a port is at the boundary of a region when it receives a legacy BPDU or an MST BPDU that is associated with a different region. However, the STP protocol migration cannot determine whether the legacy switch, which is a switch that runs only IEEE 802.1D, has been removed from the link unless the legacy switch is the designated switch. Enter this command to restart the protocol negotiation (force the renegotiation with neighboring switches) on the entire switch or on specified interfaces.

Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)

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