Configuring Spanning Tree Protocol (STP)

Maximum PORT-VLAN entries: 16

legend: [S=Slot]

PORT-VLAN 1, Name DEFAULT-VLAN, Priority level0, Spanning tree On Untagged Ports: (S3) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Untagged Ports: (S3) 17 18 19 20 21 22 23 24

Untagged Ports: (S4) 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Untagged Ports: (S4) 18 19 20 21 22 23 24 Tagged Ports: None

Uplink Ports: None

PORT-VLAN 2, Name greenwell, Priority level0, Spanning tree Off

Untagged Ports: (S1) 1 2 3 4 5 6 7 8

Untagged Ports: (S4) 1

Tagged Ports: None

Uplink Ports: None

The STP state is shown in bold type in this example.

USING THE WEB MANAGEMENT INTERFACE

To display STP information for a specific VLAN:

1.Log on to the device using a valid user name and password for read-write access. The System configuration panel is displayed.

2.Click on the plus sign next to Configure in the tree view.

3.Select the VLAN link to display the VLAN configuration options.

4.Select the Port link to display configuration information for the device’s port-based VLANs. The STP state is shown in the STP column.

Configuring Advanced Features

This section describes how to configure the following features:

•Fast Port Span

•Fast Uplink Span

•Single-instance STP

•Per VLAN Spanning Tree+ (PVST+) Compatibility

Fast Port Span

When STP is running on a device, message forwarding is delayed during the spanning tree recalculation period following a topology change. The STP forward delay parameter specifies the period of time a bridge waits before forwarding data packets. The forward delay controls the listening and learning periods of STP reconvergence. You can configure the forward delay to a value from 4 – 30 seconds. The default is 15 seconds. Thus, using the standard forward delay, convergence requires 30 seconds (15 seconds for listening and an additional 15 seconds for learning) when the default value is used.

This slow convergence is undesirable and unnecessary in some circumstances. The Fast Port Span feature allows certain ports to enter the forwarding state in four seconds. Specifically, Fast Port Span allows faster convergence on ports that are attached to end stations and thus do not present the potential to cause Layer 2 forwarding loops. Because the end stations cannot cause forwarding loops, they can safely go through the STP state changes (blocking to listening to learning to forwarding) more quickly than is allowed by the standard STP convergence time. Fast Port Span performs the convergence on these ports in four seconds (two seconds for listening and two seconds for learning).

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