Cisco Catalyst 4948 User Manual

Chapter 7: Spanning Tree Protocol (STP) 123
Section 7-2
1/1
Fwd: VLAN 100 (cost 19)
Block: VLAN 101 (cost 1000)
1/2
Block: VLAN 100 (cost 1000)
Fwd: VLAN 101 (cost 19)
Catalyst A1
Catalyst D1 Catalyst D2
19
19
19
Root
Bridge
Catalyst A1
Catalyst D1
Catalyst D2
Catalyst A1
Catalyst D1
Catalyst D2
STP Topology
VLAN 100
STP Topology
VLAN 101
Figure 7-3 Network Diagram for the STP Load-Balancing Example
Catalyst D1 can be configured with these commands:
(global) spanning-tree vlan 100 root primary
(global) spanning-tree vlan 101 root primary
Alternatively, you can explicitly set the bridge priorities with these commands (available
on all Catalyst models):
(global) spanning-tree vlan 100 priority 8192
(global) spanning-tree vlan 101 priority 8192
Catalyst D2 can be configured with these commands to become the secondary root:
(global) spanning-tree vlan 100 root secondary
(global) spanning-tree vlan 101 root secondary
Alternatively, you can explicitly set D2’s bridge priorities:
(global) spanning-tree vlan 100 priority 8200
(global) spanning-tree vlan 101 priority 8200

Cisco Catalyst 4948 Specifications

General

Switching Capacity	136 Gbps
Forwarding Rate	102 Mpps
Rack Units	1U
MAC Address Table Size	32, 000 entries
Authentication Method	RADIUS, TACACS+
RAM	256 MB
Flash Memory	64 MB
Power Device	Internal power supply
Voltage Required	100-240 VAC
Weight	16.5 lbs
Operating Humidity	10% to 85% non-condensing
Ports	48 x 10/100/1000
Power Supply	Internal
Layer Support	Layer 3
Jumbo Frame Support	Yes (up to 9216 bytes)
Routing Protocol	RIP, OSPF, EIGRP, BGP
Remote Management Protocol	SNMP, Telnet, SSH
Features	VLAN support, QoS
Compliant Standards	IEEE 802.3, IEEE 802.3u, IEEE 802.3ab, IEEE 802.1Q, IEEE 802.1p
Operating Temperature	32 °F to 104 °F (0 °C to 40 °C)