Cisco WS-SUP32-GE-3B Software Configuration Guide - Page 232

Understanding How STP Works Chapter 17 Configuring STP and MST Figure 17-4 Interface 2 in Listening State All segment frames Forwarding Station addresses Port 1 BPDUs Network management and data frames Filtering database System module Frame forwarding Data frames BPDUs Port 2 Network management frames S5693 Listening All segment frames BPDU and network management frames A Layer 2 LAN port in the listening state performs as follows: • Discards frames received from the attached segment. • Discards frames switched from another LAN port for forwarding. • Does not incorporate end station location into its address database. (There is no learning at this point, so there is no address database update.) • Receives BPDUs and directs them to the system module. • Receives, processes, and transmits BPDUs received from the system module. • Receives and responds to network management messages. Learning State A Layer 2 LAN port in the learning state prepares to participate in frame forwarding. The Layer 2 LAN port enters the learning state from the listening state. Figure 17-5 shows a Layer 2 LAN port in the learning state. 17-8 Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY OL-11439-03