Test your knowledge of Spanning Tree Protocol (STP) concepts
The Spanning Tree Protocol (STP) has been around and widely accepted for quite a while. Questions about it appear on numerous certification exams associated with networking, including the Cisco CCNA and CompTIA Network+ exams. How much do you know about STP and variants of it as well as the different technologies that surround it? How well can you answer questions on the basics of it?
What follows is a self-test of 25 questions based on the general concepts and topics related to Spanning Tree protocols, algorithms, technologies, and concepts. In all cases, pick the best answer(s) to each question. The answers appear at the end of the questions. Good luck!
1. On a Cisco switch, what effect will enabling the portfast variable on a port have?
A. The port stops forwarding in order to allow other ports to perform faster.
B. The port begins looking only at a portion of data headers in order to prioritize speed.
C. The port switches from forwarding mode to blocking mode.
D. The port switches from blocking mode to forwarding mode.
2. The head of IT security at WXS Limited has sent a note to administrators that there will be a move from PVST to PVST+ on switches because PVST+ uses better encapsulation. Which of the following does PVST+ use for VLAN encapsulation?
3. At what layer of the OSI model does STP operate?
A. Layer One
B. Layer Two
C. Layer Three
D. Layer Four
4. When there is more than one link between switches, the root bridge calculates the cost of each path based on what value?
B. number of hops
C. software version
5. Which feature on Cisco switches can be used to provide additional protection against Layer 2 forwarding loops?
A. BPDU stop
B. Rapid PVST+
D. Loop guard
6. Switches exchange information among themselves that is used in root switch selection via which of the following?
7. Each VLAN on each switch has a unique bridge ID of how many bits?
8. Which of the following will generally be the result of a failure in the Spanning Tree Algorithm?
A. Bridging loop
B. Gateway error
C. Duplicate IP addresses
D. Broadcast storm
9. When using Rapid PVST+, which of the following maps multiple VLANs into the same spanning-tree instance?
10. Which of the following is the IEEE specification for STP?
11. Which RSTP bridge port role indicates it is a redundant path to a segment where another bridge port already connects?
12. The Rapid Spanning Tree Protocol was created after STP and is:
A. a complement to STP, requiring it to also be used
B. capable of operating at Layer 4 of the OSI model
C. backward compatible with STP
D. not backward compatible with STP
13. Which of the following is a switch that can become the root bridge for a VLAN if the primary root bridge fails?
A. Subordinate root bridge
B. Secondary root bridge
C. Minor root bridge
D. Ancillary root bridge
14. On a Cisco switch, which IOS command shows a summary of connected spanning tree ports by VLAN?
A. show stp summary
B. show spanning tree
C. show spantree summary
D. show summary stp
15. Which of the following statements is true?
A. BPDU guard does not work on PortFast-enabled ports.
B. Loop guard cannot be enabled for ports on which PortFast is enabled.
C. Loop guard can be enabled on dynamic VLAN ports.
D. Neither uplink fast or backbone fast are transparent to the loop guard.
Please visit GoCertify to attempt the remaining 10 questions of this quiz.
1. D — The portfast variable switches the port immediately from blocking mode to forwarding mode.
2. B — PVST+ (Per-VLAN Spanning Tree+) uses 802.1Q VLAN encapsulation.
3. B — STP (the Spanning Tree Protocol) is a Layer 2 protocol that operates on bridges and switches.
4. A — The STP root bridge calculation is based on bandwidth.
5. D — The loop guard feature on Cisco switches can be used to provide additional protection against Layer 2 forwarding loops.
6. C — BPDUs (Bridge Protocol Data Units) are used for this information among the switches.
7. B — Each VLAN on each switch has a unique bridge ID that is 64-bits long. This ID contains the bridge priority value, an extended system ID, and an STP MAC address allocation.
8. A — Most often, a failure in the Spanning Tree Algorithm results in a bridging loop.
9. D — MSTP (Multiple Spanning Tree Protocol) maps multiple VLANs into the same spanning-tree instance.
10. A — The IEEE specification for STP is 802.1D. As such, STP will operate on devices (bridges and switches) which are 802.1D-compliant.
11. D — The backup role is used to create a redundant path to a segment where another bridge port already connects.
12. C — The Rapid Spanning Tree Protocol (RST), by design, is backwards-compatible with STP. As a result of this, RSTP will revert to STP on an interface if an STP BPDU is detected on a port.
13. B — A secondary root bridge is a switch that can become the root bridge for a VLAN if the primary root bridge fails.
14. C — On a Cisco switch, the IOS command show spantree summary shows a summary of connected spanning tree ports by VLAN.
15. B — Loop guard cannot be enabled for ports on which PortFast is enabled.