Dell PowerConnect FCS624S Configuration Guide - Page 265

Configuring STP related features 8 PowerConnect#show interface brief Port 1/1 1/2 1/3 1/4 1/5 1/6 1/7 1/8 Link State Down None Down None Down None Down None Down None Down None Down None Down None Dupl Speed Trunk Tag Priori MAC Name None None None No level0 00e0.52a9.bb00 None None None No level0 00e0.52a9.bb01 None None None No level0 00e0.52a9.bb02 None None None No level0 00e0.52a9.bb03 None None None No level0 00e0.52a9.bb04 None None None No level0 00e0.52a9.bb05 None None None No level0 00e0.52a9.bb06 None None None No level0 00e0.52a9.bb07 . . some rows omitted for brevity . 3/10 Down None None None None No level0 00e0.52a9.bb4a 3/11 Up Forward Full 100M None No level0 00e0.52a9.bb49 In the example above, only one port, 3/11, is forwarding traffic toward the root bridge. Configuring STP related features 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 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 Dell PowerConnect 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. PowerConnect B-Series FCX Configuration Guide 223 53-1002266-01