Filter
Top Products
11-9
Catalyst 2950 Desktop Switch Software Configuration Guide
78-14982-01
Chapter 11 Configuring STP
Configuring Spanning-Tree Features
Figure 11-3 Spanning Tree and Redundant Connectivity
You can also create redundant links between switches by using EtherChannel groups. For more
information, see Chapter 27, “Configuring EtherChannels.”
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, a spanning-tree 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 the spanning
tree reconfigures.
Because each VLAN is a separate spanning-tree instance, the switch accelerates aging on a per-VLAN
basis. A spanning-tree 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.
Configuring Spanning-Tree Features
These sections describe how to configure spanning-tree features:
• Default STP Configuration, page 11-10
• STP Configuration Guidelines, page 11-10
• Disabling STP, page 11-12
• Configuring the Root Switch, page 11-12
• Configuring a Secondary Root Switch, page 11-14
• Configuring the Port Priority, page 11-15
• Configuring the Path Cost, page 11-16
• Configuring the Switch Priority of a VLAN, page 11-18
Catalyst 2950 or 3550
switch
Workstations
Catalyst 2950 or 3550
switch
Catalyst 2950 or 3550
switch
Switch A
Switch B
Active link
Blocked link
Switch C
74620