CCIE Routing and Switching FAQ: Spanning Tree Protocol

ccie-routing-switching-faq-spanning-tree-protocol

CCIE Routing and Switching FAQ: Spanning Tree Protocol

Q1. Assume that a nonroot 802.1D switch has ceased to receive Hello BPDUs. Which STP setting determines how long a nonroot switch waits before trying to choose a new Root Port?
A. Hello timer setting on the Root
B. MaxAge timer setting on the Root
C. ForwardDelay timer setting on the Root
D. Hello timer setting on the nonroot switch
E. MaxAge timer setting on the nonroot switch
F. ForwardDelay timer setting on the nonroot switch

Answer: B

Q2. Assume that a nonroot 802.1D switch receives a Hello BPDU with the TCN flag set.Which STP setting determines how long the nonroot switch waits before timing out inactive CAM entries?
A. Hello timer setting on the Root
B. MaxAge timer setting on the Root
C. ForwardDelay timer setting on the Root
D. Hello timer setting on the nonroot switch
E. MaxAge timer setting on the nonroot switch
F. ForwardDelay timer setting on the nonroot switch

Answer: C

Q3. Assume that a nonroot Switch1 (SW1) is Discarding on an 802.1Q trunk connected to Switch2 (SW2). Both switches are in the same MST region. SW1 ceases to receive Hellos from SW2. What timers have an impact on how long Switch1 takes to both become the Designated Port on that link and reach the Forwarding state?
A. Hello timer setting on the Root
B. MaxAge timer setting on the Root
C. ForwardDelay timer on the Root
D. Hello timer setting on SW1
E. MaxAge timer setting on SW1
F. ForwardDelay timer on SW1

Answer: A and C

Q4. Which of the following statements are true regarding support of multiple spanning trees over an 802.1Q trunk?
A. Only one common spanning tree can be supported.

B. Cisco PVST+ supports multiple spanning trees if the switches are Cisco switches.

C. 802.1Q supports multiple spanning trees when using IEEE 802.1s MST.

D. Two PVST+ domains can pass over a region of non-Cisco switches using 802.1Q trunks by encapsulating non-native VLAN Hellos inside the native VLAN Hellos.

Answer: B and C

Q5. When a switch notices a failure, and the failure requires STP convergence, it notifies the Root by sending a TCN BPDU. Which of the following best describes why the notification is needed?
A. To speed STP convergence by having the Root converge quickly.

B. To allow the Root to keep accurate count of the number of topology changes.

C. To trigger the process that causes all switches to use a short timer to help flush the CAM.

D. There is no need for TCN today; it is a holdover from DEC’s STP specification.

Answer: C

Q6. Two switches have four parallel Ethernet segments, none of which forms into an EtherChannel. Assuming that 802.1D is in use, what is the maximum number of the eight ports (four on each switch) that stabilize into a Forwarding state?
A. 1
B. 3
C. 4
D. 5
E. 7

Answer: D

Q7. IEEE 802.1w does not use the exact same port states as does 802.1D. Which of the following are valid 802.1w port states?
A. Blocking
B. Listening
C. Learning
D. Forwarding
E. Disabled
F. Discarding

Answer: C, D, and F

Q8. What STP tools or protocols supply a “MaxAge optimization,” allowing a switch to bypass the wait for MaxAge to expire when its Root Port stops receiving Hellos?
A. Loop Guard
B. UDLD
C. BPDU Guard
D. Bridge Assurance
E. IEEE 802.1w

Answer: E

Q9. A trunk between switches lost its physical transmit path in one direction only.Which of the following features protect against the STP problems caused by such an event?
A. Loop Guard
B. UDLD
C. Dispute
D. PortFast

Answer: A, B, and C

Q10. A switch has four Ethernet segments toward its neighbor, with the intention of using them in an EtherChannel. Some settings on the physical ports on this switch might be different and yet these ports will be allowed to be bundled in a single EtherChannel. Which settings do not have to match?
A. DTP negotiation settings (auto/desirable/on)
B. Allowed VLAN list
C. STP per-VLAN port cost on the ports on a single switch
D. If 802.1Q, native VLAN

Answer: C

Q11. A computer’s NIC is hardcoded to 1000 Mbps and full-duplex, and it is connected to a switch whose Fast Ethernet interface is set to autonegotiate speed and duplex.What speed and duplex will the switch use if the autonegotiation on the computer’s NIC is deactivated as a result of hardcoding the speed and duplex?
A. 100 Mbps and full-duplex
B. 100 Mbps and half-duplex
C. 1000 Mbps and full-duplex
D. 1000 Mbps and half-duplex
E. The link will be inactive.

Answer: D

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