Page 77 - Handout Computer Network.
P. 77
Figure 3-22 shown a BPDU Communication
Figure 3-23 shown a BPDU Protocol Layout
Consequently, switches have five operating modes:
• Blocking—A port in blocking state sends and listens to BPDUs but does not forward
frames. By default, all ports are in blocking state when the switch is turned on.
• Listening—In listening state, a port listens to the BPDUs to make sure there are no
loops on the network. No frames are forwarded in this state.
• Learning—In this state, a port learns MAC addresses and builds a address table,
but it does not forward frames.
• Forwarding—A port in the forwarding state forwards frames. BPDUs are sent and
listened to.
• Disabled—A port in the disabled state does not participate in the operation of STP.
77
