3Com 5500G-EI Command Reference Guide - Page 330

334 CHAPTER 10: USING RSTP COMMANDS Description Use the stp root primary command to configure the current Switch as the primary root of a spanning tree. Use the undo stp root command to cancel the current Switch for primary root of a spanning tree. By default, the Switch is not a primary root. You can designate a primary root for the spanning tree without caring about the priority configuration of the Switch. CAUTION: In a switching network, you can configure no more than one primary root for a spanning tree but you can configure one or more secondary roots for it. Remember not to designate more than one primary root in a spanning tree; otherwise, the switching behavior will be unpredictable. After a Switch is configured as a primary root bridge or secondary root bridge, you can not modify the bridge priority of the Switch. Example To designate the current Switch as the primary root of a spanning tree, enter the following: system-view System View: return to User View with Ctrl+Z. [SW5500]stp root primary stp root secondary Syntax stp root secondary undo stp root View System view Parameter None Description Use the stp root secondary command to configure the current Switch as a secondary root of a specified spanning tree. Use the undo stp root command to cancel the designation of the current Switch for a secondary root of a specified spanning tree. By default, a Switch is not a secondary root. You can designate one or more secondary roots for a spanning tree. When the primary root fails or is powered off, a secondary root can take its place. If more than one secondary root exists, the one with the smallest MAC address will become the primary root of the specified spanning tree.