Cisco 7609 User Manual

15-7
Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
78-14064-04
Chapter 15 Configuring STP and IEEE 802.1s MST
Understanding How STP Works
Figure 15-2 STP Layer 2 LAN Interface States
When you enable STP, every port in the Cisco 7600 series router, VLAN, and network goes through the
blocking state and the transitory states of listening and learning at power up. If properly configured, each
Layer 2 LAN port stabilizes to the forwarding or blocking state.
When the STP algorithm places a Layer 2 LAN port in the forwarding state, the following process
occurs:
1. The Layer 2 LAN port is put into the listening state while it waits for protocol information that
suggests it should go to the blocking state.
2. The Layer 2 LAN port waits for the forward delay timer to expire, moves the Layer 2 LAN port to
the learning state, and resets the forward delay timer.
3. In the learning state, the Layer 2 LAN port continues to block frame forwarding as it learns end
station location information for the forwarding database.
4. The Layer 2 LAN port waits for the forward delay timer to expire and then moves the Layer 2 LAN
port to the forwarding state, where both learning and frame forwarding are enabled.
Boot-up
initialization
Blocking
state
S5691
Listening
state
Disabled
state
Learning
state
Forwarding
state

Cisco 7609 Specifications

General

Chassis Slots	9
Switch Fabric Capacity	720 Gbps
Power Supply Options	AC or DC
Product Type	Router
Form Factor	Rack-mountable
Supported Line Cards	Various Cisco 7600 Series line cards
Operating System	Cisco IOS
Management	CLI, SNMP
Forwarding Performance	400 Mpps
Maximum Power Consumption	4000 Watts
Redundancy	Yes
Interfaces/Ports	Various, depending on line cards installed