DRAG DROP
Drag the port states to their correct description.
Answer: 
Explanation:
After the bridges have determined which ports are Root Ports, Designated Ports, and nonDesignated Ports, STP is ready to create a loop-free topology. To do this, STP configures Root
Ports and Designated Ports to forward traffic. STP sets non-Designated Ports to block traffic.
Although Forwarding and Blocking are the only two states commonly seen in a stable network,
there are actually five STP states.
This list can be viewed hierarchically in that bridge ports start at the Blocking state and work their
way up to the Forwarding state. The Disabled state is the administratively shutdown STP state. It
is not part of the normal STP port processing. After the switch is initialized, ports start in the
Blocking state. The Blocking state is the STP state in which a bridge listens for BPDUs.
A port in the Blocking state does the following:
• Discards frames received from the attached segment or internally forwarded through switching
• Receives BPDUs and directs them to the system module
• Has no address database
• Does not transmit BPDUs received from the system module
• Receives and responds to network management messages but does not transmit them
If a bridge thinks it is the Root Bridge immediately after booting or in the absence of BPDUs for a
certain period of time, the port transitions into the Listening state. The Listening state is the STP
state in which no user data is being passed, but the port is sending and receiving BPDUs in an
effort to determine the active topology.
A port in the Listening state does the following:
• Discards frames received from the attached segment or frames switched from another port
• Has no address database• Receives BPDUs and directs them to the system module
• Processes BPDUs received from the system module (Processing BPDUs is a separate action
from receiving or transmitting BPDUs)
• Receives and responds to network management messages
It is during the Listening state that the three initial convergence steps take place – elect a Root
Bridge, elect Root Ports, and elect Designated Ports. Ports that lose the Designated Port election
become non-Designated Ports and drop back to the Blocking state. Ports that remain Designated
Ports or Root Ports after 15 seconds – the default Forward Delay STP timer value – progress into
the Learning state. The lifetime of the Learning state is also governed by the Forward Delay timer
of 15 seconds, the default setting.
The Learning state is the STP state in which the bridge is not passing user data frames but is
building the bridging table and gathering information, such as the source VLANs of data frames.
As the bridge receives a frame, it places the source MAC address and port into the bridging table.
The Learning state reduces the amount of flooding required when data forwarding begins.
A port in the Learning state does the following:
If a port is still a Designated Port or Root Port after the Forward Delay timer expires for the
Learning state, the port transitions into the Forwarding state. The Forwarding state is the STP
state in which data traffic is both sent and received on a port. It is the “last” STP state. At this
stage, it finally starts forwarding user data frames.
A port in the Forwarding state does the following:
Reference:
CCNP BCMSN Official Exam Certification Guide, Fourth Edition, Chapter 8: Traditional Spanning
Tree Protocol, IEEE 802.1D Overview, p. 197
