Cisco Catalyst 2950 User Manual

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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 14 Configuring MSTP
Configuring MSTP Features
• Propagation—When an RSTP switch receives a TC message from another switch through a
designated or root port, it propagates the change to all of its nonedge, designated ports and to the
root port (excluding the port on which it is received). The switch starts the TC-while timer for all
such ports and flushes the information learned on them.
• Protocol migration—For backward compatibility with IEEE 802.1D switches, RSTP selectively
sends IEEE 802.1D configuration BPDUs and TCN BPDUs on a per-port basis.
When a port is initialized, the migrate-delay timer is started (specifies the minimum time during
which RSTP BPDUs are sent), and RSTP BPDUs are sent. While this timer is active, the switch
processes all BPDUs received on that port and ignores the protocol type.
If the switch receives an IEEE 802.1D BPDU after the port migration-delay timer has expired, it
assumes that it is connected to an IEEE 802.1D switch and starts using only IEEE 802.1D BPDUs.
However, if the RSTP switch is using IEEE 802.1D BPDUs on a port and receives an RSTP BPDU
after the timer has expired, it restarts the timer and starts using RSTP BPDUs on that port.
Configuring MSTP Features
These sections describe how to configure basic MSTP features:
• Default MSTP Configuration, page 14-12
• MSTP Configuration Guidelines, page 14-12
• Specifying the MST Region Configuration and Enabling MSTP, page 14-13 (required)
• Configuring the Root Switch, page 14-14 (optional)
• Configuring a Secondary Root Switch, page 14-16 (optional)
• Configuring the Port Priority, page 14-17 (optional)
• Configuring the Path Cost, page 14-18 (optional)
• Configuring the Switch Priority, page 14-19 (optional)
• Configuring the Hello Time, page 14-19 (optional)
• Configuring the Forwarding-Delay Time, page 14-20 (optional)
• Configuring the Maximum-Aging Time, page 14-21 (optional)
• Configuring the Maximum-Hop Count, page 14-21 (optional)
• Specifying the Link Type to Ensure Rapid Transitions, page 14-22 (optional)
• Restarting the Protocol Migration Process, page 14-22 (optional)

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