Accelerated Aging To Retain Connectivity; Understanding Advanced Stp Features; Stp And Redundant Connectivity - Cisco Catalyst 2950 Software Manual

Chapter 9 Configuring STP
Figure 9-3
Catalyst 2950
Catalyst 2950
You can also create redundant links between switches by using EtherChannel groups. For more
information, see the

Accelerated Aging to Retain Connectivity

The default for aging dynamic addresses is 5 minutes, the default setting of the mac-address-table
aging-time global configuration command. However, an STP reconfiguration can cause many station
locations to change. Because these stations could be unreachable for 5 minutes or more during a
reconfiguration, the address-aging time is accelerated so that station addresses can be dropped from the
address table and then relearned. The accelerated aging is the same as the forward-delay parameter value
(spanning-tree vlan vlan-id forward-time seconds global configuration command) when STP
reconfigures.
Because each VLAN is a separate spanning-tree instance, the switch accelerates aging on a per-VLAN
basis. An STP reconfiguration on one VLAN can cause the dynamic addresses learned on that VLAN to
be subject to accelerated aging. Dynamic addresses on other VLANs can be unaffected and remain
subject to the aging interval entered for the switch.

Understanding Advanced STP Features

This section describes how advanced STP features work. It includes this information:
•
•
•
•
•
•
For configuration information, see the
78-11380-03

STP and Redundant Connectivity

Switch A
switch
switch
Switch B
Active link
Blocked link
Chapter 10, "Configuring the Switch Ports."
Understanding Port Fast, page 9-10
Understanding BPDU Guard, page 9-10
Understanding UplinkFast, page 9-11
Understanding Cross-Stack UplinkFast, page 9-12
Understanding BackboneFast, page 9-17
Understanding Root Guard, page 9-19
Switch C
Workstations
"Configuring Advanced STP Features" section on page
Catalyst 2950 Desktop Switch Software Configuration Guide
Understanding Advanced STP Features
Catalyst 2950
switch
9-30.
9-9