KB.15.15

100 Mbps 200000

1 Gbps 20000

Default: Auto

Informing the switch of the device type to which a port connects

Syntax:

spanning-tree port-list point-to-point-mac [ true | false | auto ]

Informs the switch of the type of device to which a specific port connects.

true (Default) Indicates a point-to-point link to a device such as a switch, bridge,

or end-node.

false Indicates a connection to a half-duplex repeater (which is a shared LAN

segment).

auto Causes the switch to set Force-False on the port if it is not running at full

duplex.

Determining which port to use for forwarding

Syntax:

spanning-tree port-list priority priority-multiplier

MSTP uses this parameter to determine the port to use for forwarding. The port with

the lowest priority number has the highest priority for use.

The range is 0 to 240, and is configured by specifying a multiplier from 0 - 15.

When you specify a priority multiplier of 0 - 15, the actual priority assigned to the

switch is:

(priority-multiplier) x 16

If you configure 2 as the priority multiplier on a given port, the actual Priority setting

is 32. After specifying the port priority multiplier, the switch displays the actual port

priority (and not the multiplier) in the show spanning-tree or show

spanning-tree port-list displays.

You can view the actual multiplier setting for ports by executing show running

and looking for an entry in this format:

spanning-tree port-list priority priority-multiplier

For example, configuring port A2 with a priority multiplier of 3 results in the following

line in the show running output:

spanning-tree A2 priority 3

Denying a port the role of root port

Syntax:

spanning-tree port-list root-guard

When a port is enabled as root-guard, it cannot be selected as the root port

even if it receives superior STP BPDUs. The port is assigned an "alternate" port role

and enters a blocking state if it receives superior STP BPDUs.

A superior BPDU contains both "better" information on the root bridge and path

cost to the root bridge, which would normally replace the current root bridge

selection.

Configuring MSTP per-port parameters 85