Cisco NME-16ES-1G User Guide - Page 17

16- and 36-Port Ethernet Switch Module for Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Feature Overview Listening State The listening state is the first transitional state a Layer 2 interface enters after the blocking state. The Layer 2 interface enters this state when STP determines that the Layer 2 interface should participate in frame forwarding. Figure 6 shows a Layer 2 interface in the listening state. Figure 6 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 interface in the listening state performs as follows: • Discards frames received from the attached segment. • Discards frames switched from another interface 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. Cisco IOS Release 12.2(2)XT, 12.2(8)T, and 12.2(15)ZJ 17