Cisco Catalyst 2950 Software Guide

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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 9 Configuring STP
Configuring Advanced STP Features
Configuring BackboneFast
You can enable BackboneFast to detect indirect link failures and to start the spanning-tree
reconfiguration sooner.
Note If you use BackboneFast, you must enable it on all switches in the network. BackboneFast is not
supported on Token Ring VLANs. This feature is supported for use with third-party switches.
Beginning in privileged EXEC mode, follow these steps to enable BackboneFast:
To disable the BackboneFast feature, use the no spanning-tree backbonefast global configuration
command.
Configuring Root Guard
Root guard enabled on an interface applies to all the VLANs to which the interface belongs. Each VLAN
has its own spannning-tree instances.
Do not enable the root guard on interfaces to be used by the UplinkFast feature. With UplinkFast, the
backup interfaces (in the blocked state) replace the root port in the case of a failure. However, if root
guard is also enabled, all the backup interfaces used by the UplinkFast feature are placed in the
root-inconsistent state (blocked) and are prevented from reaching the forwarding state.
Beginning in privileged EXEC mode, follow these steps to enable root guard on an interface:
To disable the root guard feature, use the no spanning-tree guard or the spanning-tree guard none
interface configuration commands.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
spanning-tree backbonefast Enable BackboneFast on the switch.
Step 3
end Return to privileged EXEC mode.
Step 4
show spanning-tree vlan vlan-id Verify your entries.
Step 5
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
interface interface-id Enter interface configuration mode, and specify an interface to
configure. Valid interfaces include physical interfaces and
port-channel logical interfaces (port-channel port-channel-number).
Step 3
spanning-tree guard root Enable root guard on the interface.
By default, root guard is disabled on all interfaces.
Step 4
end Return to privileged EXEC mode.
Step 5
show running-config Verify your entries.
Step 6
copy running-config startup-config (Optional) Save your entries in the configuration file.

Cisco Catalyst 2950 Specifications

General

Forwarding Bandwidth	8.8 Gbps
Switching Capacity	13.6 Gbps
Forwarding Rate	6.6 Mpps
Weight	3.6 kg
RAM	16 MB
Flash Memory	8 MB
Operating Humidity	10% to 85% non-condensing
Uplink Ports	2 x 10/100/1000Base-T
Dimensions	4.4 cm x 44.5 cm x 24.2 cm
Remote Management Protocol	SNMP, Telnet, HTTP
Features	Quality of Service (QoS), VLAN support
Compliant Standards	IEEE 802.3, IEEE 802.3u, IEEE 802.1D, IEEE 802.1Q, IEEE 802.1p
Status Indicators	system
Operating Temperature	0 to 45°C
Ports	24 x 10/100 Ethernet ports
MAC Address Table Size	8, 192 entries
Power Supply	Internal 100-240V AC, 50-60Hz