Spanning Tree Algorithm Configuration 3

•Migration – If at any time the switch detects STP BPDUs, including Configuration or Topology Change Notification BPDUs, it will automatically set the selected interface to forced STP-compatible mode. However, you can also use the Protocol Migration button to manually re-check the appropriate BPDU format (RSTP or STP-compatible) to send on the selected interfaces. (Default: Disabled)

Web – Click Spanning Tree, STA, Port Configuration or Trunk Configuration. Modify the required attributes, then click Apply.

Figure 3-70 STA Port Configuration

CLI – This example sets STA attributes for port 7.

Console(config)#interface ethernet 1/7

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Console(config-if)#no spanning-tree spanning-disabled

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Console(config-if)#spanning-tree port-priority 0

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Console(config-if)#spanning-tree cost 50

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Console(config-if)#spanning-tree link-type auto

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Console(config-if)#no spanning-tree edge-port

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Console(config-if)#spanning-tree protocol-migration

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Configuring Multiple Spanning Trees

MSTP generates a unique spanning tree for each instance. This provides multiple pathways across the network, thereby balancing the traffic load, preventing wide-scale disruption when a bridge node in a single instance fails, and allowing for faster convergence of a new topology for the failed instance.

By default all VLANs are assigned to the Internal Spanning Tree (MST Instance 0) that connects all bridges and LANs within the MST region. This switch supports up to 65 instances. You should try to group VLANs which cover the same general area of your network. However, remember that you must configure all bridges within the same MSTI Region (page 3-118)with the same set of instances, and the same instance (on each bridge) with the same set of VLANs. Also, note that RSTP treats each MSTI region as a single node, connecting all regions to the Common Spanning Tree.

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