Ditka - ICND2 - Chapter 2

Question 1

Which of the following IEEE 802.1D port states are stable states used when STP has completed convergence? (Choose two answers.)

a) Blocking
b) Forwarding
c) Listening
d) Learning
e) Discarding

Answer 1

A, B. Listening and learning are transitory port states, used only when moving from the blocking to the forwarding state. Discarding is not an 802.1D STP port state.

Question 2

Which of the following are transitory IEEE 802.1D port states used only during the process of STP convergence? (Choose two answers.)

a) Blocking
b) Forwarding
c) Listening
d) Learning
e) Discarding

Answer 2

C, D. Listening and learning are transitory port states, used only when moving from the blocking to the forwarding state. Discarding is not an 802.1D STP port state. Forwarding and blocking are stable states.

Question 3

Which of the following bridge IDs wins election as root, assuming that the switches with these bridge IDs are in the same network?

a) 32769:0200.1111.1111
b) 32769:0200.2222.2222
c) 4097:0200.1111.1111
d) 4097:0200.2222.2222
e) 40961:0200.1111.1111

Answer 3

C. The smallest numeric bridge ID wins the election.

Question 4

Which of the following facts determines how often a nonroot bridge or switch sends an 802.1D STP Hello BPDU Message?

a) The Hello timer as configured on that switch.
b) The Hello timer as configured on the root switch.
c) It is always every 2-seconds.
d) The switch reacts to BPDUs received from the root switch by sending another BPDU 2 seconds after receiving the root BPDU.

Answer 4

B. Nonroot switches forward Hellos received from the root; the root sends these Hellos based on the root’s configured Hello timer.

Question 5

Which of the following RSTP port states have the same name and purpose as a port state in traditional 802.1D STP? (Choose two answers.)

a) Blocking
b) Forwarding
c) Listening
d) Learning
e) Discarding

Answer 5

B, D. RSTP uses port states forwarding, learning, and discarding. Forwarding and learning perform the same functions as the port states used by traditional 802.1D STP.

Question 6

RSTP adds some concepts to STP that enable ports to be used for a role if another port on the same switch fails. Which of the following statements correctly describe a port role that is waiting to take over for another port role? (Choose two answers.)

a) An alternate port waits to become a root port.
b) A backup port waits to become a root port.
c) An alternate port waits to become a designated port.
d) A backup waits to become a designated port.

Answer 6

A, D. With RSTP, an alternate port is an alternate to the root port when a switch’s root port fails. A backup port takes over for a designated port if the designated port fails.

Question 7

What STP feature causes an interface to be placed in the forwarding state as soon as the interface is physically active?

a) STP
b) EtherChannel
c) Root Guard
d) PortFast

Answer 7

D. The PortFast feature allows STP to move a port from blocking to forwarding, without going through the interim listening and learning states. STP allows this exception
when the link is known to have no switch on the other end of the link, removing the risk of a switching loop. BPDU Guard is a common feature to use at the same time as PortFast, because it watches for incoming bridge protocol data units (BPDU), which should not happen on an access port, and prevents the loops from a rogue switch by disabling the port.