Cisco Systems 3750E manual Designating the Neighbor Type, 19-25

Chapter 19 Configuring MSTP

Configuring MSTP Features

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 running MSTP, you can override the default setting of the link type and enable rapid transitions to the forwarding state.

Beginning in privileged EXEC mode, follow these steps to override the default link-type setting. This procedure is optional.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	interface interface-id	Specify an interface to configure, and enter interface
		configuration mode. Valid interfaces include physical ports,
		VLANs, and port-channel logical interfaces. The VLAN ID
		range is 1 to 4094. The port-channel range is 1 to 48.
Step 3
	spanning-tree link-type point-to-point	Specify that the link type of a port is point-to-point.
Step 4
	end	Return to privileged EXEC mode.
Step 5
	show spanning-tree mst interface interface-id	Verify your entries.
Step 6
	copy running-config startup-config	(Optional) Save your entries in the configuration file.

To return the port to its default setting, use the no spanning-treelink-typeinterface configuration command.

Designating the Neighbor Type

A topology could contain both prestandard and IEEE 802.1s standard compliant devices. By default, ports can automatically detect prestandard devices, but they can still receive both standard and prestandard BPDUs. When there is a mismatch between a device and its neighbor, only the CIST runs on the interface.

You can choose to set a port to send only prestandard BPDUs. The prestandard flag appears in all the show commands, even if the port is in STP compatibility mode.

Beginning in privileged EXEC mode, follow these steps to override the default link-type setting. This procedure is optional.

	Command	Purpose
Step 1
	configure terminal	Enter global configuration mode.
Step 2
	interface interface-id	Specify an interface to configure, and enter interface
		configuration mode. Valid interfaces include physical ports.
Step 3
	spanning-tree mst pre-standard	Specify that the port can send only prestandard BPDUs.
Step 4
	end	Return to privileged EXEC mode.
Step 5
	show spanning-tree mst interface interface-id	Verify your entries.
Step 6
	copy running-config startup-config	(Optional) Save your entries in the configuration file.
	To return the port to its default setting, use the no spanning-tree mst prestandard interface
	configuration command.
		Catalyst 3750-E and 3560-E Switch Software Configuration Guide
OL-9775-02			19-25