Cisco WS-C2948G-GE-TX - Understanding How PVST+ and MISTP Modes Work

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Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
78-15908-01
Chapter 7 Configuring Spanning Tree
Understanding How PVST+ and MISTP Modes Work
Disabled State
A port in the disabled state does not participate in frame forwarding or STP, as shown in Figure 7-7. A
port in the disabled state is virtually nonoperational.
Figure 7-7 Port 2 in Disabled State
A disabled port performs as follows:
• Discards frames that are received from the attached segment
• Discards frames that are switched from another port for forwarding
• Does not incorporate station location into its address database (there is no learning, so there is no
address database update)
• Receives BPDUs but does not direct them to the system module
• Does not receive BPDUs for transmission from the system module
• Receives and responds to network management messages
Understanding How PVST+ and MISTP Modes Work
Catalyst 4500 series switches provide two proprietary spanning tree modes based on the IEEE 802.1D
standard and one mode that is a combination of the two modes:
• Per VLAN Spanning Tree (PVST+)
• Rapid PVST+
• Multi-Instance Spanning Tree Protocol (MISTP)
• MISTP-PVST+ (combination mode)
Filtering
database
Frame
forwarding
System
module
Port 1
BPDUs
All segment
frames
All segment
frames
Forwarding
Disabled
Station
addresses
Network
management
and data frames
Port 2
S5696
Network
management
frames
Data
frames