ADTRAN 1000R Series - Manual (Page 780)

Command Reference Guide ATM Sub-Interface Config Command Set
61200510L1-35E Copyright © 2005 ADTRAN 780
spanning-tree path-cost <value>
Use the spanning tree path-cost command to assign a cost to a bridge group that is used when computing
the spanning-tree root path. To return to the default path-cost value, use the no form of this command.
Syntax Description
<value> Assigns number to the bridge interface to be used as the path cost in spanning
calculations (valid range: 0 to 65,535).
Default Values
By default, the path-cost value is set to 19.
Applicable Platforms
This command applies to the NetVanta 300, 1000R, 3000, and 4000 Series units.
Command History
Release 1.1 Command was introduced.
Release 8.1 ATM sub-interface was added.
Functional Notes
The specified value is inversely proportional to the likelihood the bridge interface will be chosen as the root
path. Set the path-cost value lower to increase the chance the interface will be the root. To obtain the most
accurate spanning tree calculations, develop a system for determining path costs for links and apply it to all
bridged interfaces.
Usage Examples
The following example assigns a path cost of 100 for bridge group 17 on an ATM sub-interface:
(config)#interface atm 1.1
(config-atm 1.1)#spanning-tree path-cost 100
Technology Review
Spanning-tree protocol provides a way to prevent loopback or parallel paths in bridged networks. Using the
priority values and path costs assigned to each bridging interface, the spanning-tree protocol determines
the root path and identifies whether to block or allow other paths.