VDV Network Infrastructure 4 — Questions and Answers
Question 1: What is the function of Spanning Tree Protocol (STP) in a switched network?
- Assigns IP addresses to devices automatically
- Prevents Layer 2 switching loops by blocking redundant paths (Correct answer)
- Encrypts traffic between switches
- Aggregates multiple switch uplinks for higher bandwidth
Correct answer: Prevents Layer 2 switching loops by blocking redundant paths
STP prevents broadcast storms caused by Layer 2 loops by electing a root bridge and placing redundant ports in a blocking state.
Question 2: A coaxial cable run in a CATV distribution system shows excessive signal loss. Which tool would best identify the fault location?
- Cable certifier
- Time Domain Reflectometer (TDR) (Correct answer)
- Tone generator and probe
- Optical power meter
Correct answer: Time Domain Reflectometer (TDR)
A TDR sends a signal pulse down the cable and measures the time for reflections to return, identifying faults, shorts, or impedance mismatches and their distance.
Question 3: In a PoE installation, what is the maximum power a PoE+ (802.3at) switch port can deliver to a powered device?
- 7.5 watts
- 15.4 watts
- 30 watts (Correct answer)
- 60 watts
Correct answer: 30 watts
PoE+ (802.3at Type 2) delivers up to 30 watts at the powered device (PD), compared to 15.4 watts for standard PoE (802.3af).
Question 4: What is the purpose of a demarcation point (demarc) in a building's network infrastructure?
- Separates the ISP's responsibility from the customer's internal network (Correct answer)
- Marks where fiber converts to copper cabling
- Indicates the center of the cable run for length calculations
- Separates the voice network from the data network
Correct answer: Separates the ISP's responsibility from the customer's internal network
The demarc is the physical boundary where the service provider's network ends and the customer's premises wiring begins, defining ownership and maintenance responsibility.
Question 5: Which grounding conductor is used to bond the telecommunications equipment rack to the building's grounding system?
- Telecommunications Bonding Backbone (TBB) (Correct answer)
- Equipment Ground Wire (EGW)
- Isolated Ground (IG) conductor
- Neutral bonding conductor
Correct answer: Telecommunications Bonding Backbone (TBB)
The Telecommunications Bonding Backbone (TBB) connects the telecommunications main grounding busbar (TMGB) to intermediate grounding busbars (TGB) throughout the building.
Question 6: What is the recommended maximum pulling tension for a 4-pair Cat6 UTP cable during installation?
- 10 lbs (44 N)
- 25 lbs (110 N) (Correct answer)
- 50 lbs (222 N)
- 75 lbs (334 N)
Correct answer: 25 lbs (110 N)
TIA-568 limits pulling tension to 25 lbs (110 N) for 4-pair UTP to prevent stretching of the conductors or deformation of the pair geometry.
Question 7: A VDV technician is installing a wireless access point that requires 802.3bt (PoE++) power. What is the maximum power delivered at the device?
- 30 watts
- 60 watts
- 90 watts (Correct answer)
- 100 watts
Correct answer: 90 watts
802.3bt Type 3 (PoE++) delivers up to 60 watts and Type 4 delivers up to 90 watts at the powered device, supporting high-power APs and other devices.
VDV Network Infrastructure 4
What is the function of Spanning Tree Protocol (STP) in a switched network?