Newsgroup: it.comp.reti.cisco
Titolo: Spanning tree: BPDU e listening state

Non riesco a capire se i BPDU vengono inviati e ricevuti durante la
fase di listening.
Il mio libro (ciscopress self-study) dice che vengono inviati, dal sito
cisco però non emerge.
A rigor di logica, se durante la fase di listening si compiono
l'elezione del RootBridge e la definizione delle
porte(root,designated,non-designated) mi sembra improbabile che i bpdu
non vengano inviati. La differenza sostanziale tra listening e learning
sarebbe quindi il "popolamento" della CAM.
Da:
http://www.cisco.com/univercd/cc/td/doc/product/rtrmgmt/sw_ntman/cwsimain/cwsi2/cwsiug2/vlan2/stpapp.htm
Listening State
The listening state is the first transitional state a port enters after
the blocking state, when Spanning-Tree Protocol determines that the
port should participate in frame forwarding. Learning is disabled in
the listening state. Figure C-5 shows a port in the listening state.
A port in the listening state performs as follows:
-Discards frames received from the attached segment.
-Discards frames switched from another port for forwarding.
-Does not incorporate 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.
-Processes BPDUs received from the system module.
-Receives and responds to network management messages.
Learning State
A port in the learning state is preparing to participate in frame
forwarding. This is the second transitional state through which a port
moves in anticipation of frame forwarding. The port enters the learning
state from the listening state through the operation of Spanning-Tree
Protocol.
A port in the learning state performs as follows:
-Discards frames received from the attached segment.
-Discards frames switched from another port for forwarding.
-Incorporates station location into its address database.
-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.
Aspetto vostri commenti
Marco

Dal cisco academy curriculum ver4.0:
Each Layer 2 port on a switch running STP exists in one of these five
port states:
Blocking - In this state, the Layer 2 port is a nondesignated port
and does not participate in frame forwarding. The port receives BPDUs
to determine the location and Root ID of the root switch and what port
roles (root, designated, or nondesignated) each switch port should
assume in the final active STP topology.
Listening - In this state, spanning tree has determined that the port
can participate in frame forwarding according to the BPDUs that the
switch has received thus far. At this point, the switch port is not
only receiving BPDUs, it is also transmitting its own BPDUs and
informing adjacent switches that the switch port is preparing to
participate in the active topology.
Learning - In this state, the Layer 2 port prepares to participate in
frame forwarding and begins to populate the CAM table. Forwarding -
In this state, the Layer 2 port is considered part of the active
topology and forwards frames and also sends and receives BPDUs.
Disabled - In this state, the Layer 2 port does not participate in
spanning tree and does not forward frames.