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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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