Brocade FastIron Ethernet Switch Platform and Layer 2 Switching Configuration Guide - Manual (Page 266)

You also can display the STP states of all ports by entering the show interface brief command such as
the following, which uses the brief parameter.
device#show interface brief
Port Link State Dupl Speed Trunk Tag Priori MAC Name
1/1 Down None None None None No level0 0000.00a9.bb00
1/2 Down None None None None No level0 0000.00a9.bb01
1/3 Down None None None None No level0 0000.00a9.bb02
1/4 Down None None None None No level0 0000.00a9.bb03
1/5 Down None None None None No level0 0000.00a9.bb04
1/6 Down None None None None No level0 0000.00a9.bb05
1/7 Down None None None None No level0 0000.00a9.bb06
1/8 Down None None None None No level0 0000.00a9.bb07
.
. some rows omitted for brevity
.
3/10 Down None None None None No level0 0000.00a9.bb4a
3/11 Up Forward
Full 100M None No level0 0000.00a9.bb49
In the example above, only one port, 3/11, is forwarding traffic toward the root bridge.
STP feature configuration
Spanning Tree Protocol (STP) features extend the operation of standard STP, enabling you to fine-
tune standard STP and avoid some of its limitations.
This section describes how to configure these parameters on Brocade Layer 3 Switches using the CLI.
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).
In addition, Fast Port Span enhances overall network performance in the following ways:
• Fast Port Span reduces the number of STP topology change notifications on the network. When an
end station attached to a Fast Span port comes up or down, the Brocade device does not generate
a topology change notification for the port. In this situation, the notification is unnecessary since a
change in the state of the host does not affect the network topology.
• Fast Port Span eliminates unnecessary MAC cache aging that can be caused by topology change
notifications. Bridging devices age out the learned MAC addresses in their MAC caches if the
addresses are unrefreshed for a given period of time, sometimes called the MAC aging interval.
When STP sends a topology change notification, devices that receive the notification use the value
of the STP forward delay to quickly age out their MAC caches. For example, if a device normal
STP feature configuration
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