66Configuring the current device as a secondary root bridge of a specific spanning treeFollow these steps to configure the current device as a secondary root bridge of a specific spanning tree:To do… Use the command… RemarksEnter system view system-view —Configure the current device as asecondary root bridge• In STP/RSTP mode:stp root secondary• In PVST mode:stp vlan vlan-list root secondary• In MSTP mode:stp [ instance instance-id ] rootsecondaryRequiredUse one of the commands.By default, a device does notfunction as a secondary rootbridge.NOTE:• You can specify one root bridge for each spanning tree, regardless of the device priority settings. Onceyou specify a device as the root bridge or a secondary root bridge, you cannot change its priority.• You can configure the current device as the root bridge by setting the device priority to 0. For the devicepriority configuration, see "Configuring the device priority."Configuring the device priorityPriority is a factor in spanning tree calculation. The priority of a device determines whether the devicecan be elected as the root bridge of a spanning tree. A lower numeric value indicates a higher priority.You can set the priority of a device to a low value to specify the device as the root bridge of the spanningtree. A spanning tree device can have different priorities in different MSTIs.Follow these steps to configure the priority of a device in a specified MSTI:To do… Use the command… RemarksEnter system view system-view —Configure the priority of thecurrent device• In STP/RSTP mode:stp priority priority• In PVST mode:stp vlan vlan-list priority priority• In MSTP mode:stp [ instance instance-id ] prioritypriorityRequiredUse one of the commands.The default setting is 32768.NOTE:• You cannot change the priority of a device after it is configured as the root bridge or as a secondary rootbridge.• During root bridge selection, if all devices in a spanning tree have the same priority, the one with thelowest MAC address will be selected as the root bridge of the spanning tree.
