RCDD (RCDD): Network Design Principles and Practice 4 — Questions and Answers
Question 1: A healthcare facility requires in-building wireless coverage for 802.11ax (Wi-Fi 6). Which cabling infrastructure consideration is most critical for the access point (AP) deployment?
- Using plenum-rated Cat 5e cable
- Ensuring each AP has a dedicated Cat 6A or higher horizontal run with PoE++ capability (Correct answer)
- Installing coaxial cable to each AP location
- Providing a separate conduit for each AP
Correct answer: Ensuring each AP has a dedicated Cat 6A or higher horizontal run with PoE++ capability
Wi-Fi 6 APs with multiple radios and MIMO antennas often require high PoE wattage (802.3bt Type 3/4); Cat 6A minimizes PoE heat rise and supports future bandwidth needs.
Question 2: An RCDD must specify fire-stopping for cable penetrations through a 2-hour rated fire wall. Which action satisfies the NEC and life safety requirements?
- Installing metal conduit through the wall
- Using listed firestop materials to restore the fire resistance rating at each penetration (Correct answer)
- Routing cables through the ceiling plenum to avoid the wall
- Applying electrical tape around the cable bundle
Correct answer: Using listed firestop materials to restore the fire resistance rating at each penetration
Listed firestop systems (putty, pillows, sealants) must be installed at every penetration to restore the wall's fire resistance rating as required by NEC Article 300 and NFPA 101.
Question 3: What does the term 'alien crosstalk' (AXT) refer to in structured cabling?
- Crosstalk between pairs within the same cable
- Crosstalk between adjacent cables in a bundle or pathway (Correct answer)
- Signal reflection at connector interfaces
- Electromagnetic interference from external sources
Correct answer: Crosstalk between adjacent cables in a bundle or pathway
Alien crosstalk is electromagnetic coupling between conductors in different cables routed in close proximity, which becomes a limiting factor for 10GBASE-T over Cat 6 cabling.
Question 4: In designing a pathway for telecommunications cables through a ceiling plenum, which cable type is required by NFPA 70 when no conduit is used?
- CM-rated cable
- CMR (riser) rated cable
- CMP (plenum) rated cable (Correct answer)
- CATV coaxial cable
Correct answer: CMP (plenum) rated cable
NEC Article 800 requires CMP-rated (plenum) cable in air-handling spaces because it produces less smoke and toxic gases if ignited.
Question 5: Which design approach should an RCDD recommend to minimize electromagnetic interference (EMI) when routing data cabling parallel to electrical power conductors?
- Use smaller gauge copper conductors
- Maintain the minimum separation distances specified in TIA-569 and run cables at right angles where crossings occur (Correct answer)
- Use only fiber optic cable throughout the building
- Install data cables inside metallic conduit only near elevators
Correct answer: Maintain the minimum separation distances specified in TIA-569 and run cables at right angles where crossings occur
TIA-569 specifies minimum separation distances between power and telecommunications pathways, and perpendicular crossings further reduce inductive coupling.
Question 6: A client requests a network design that supports 25GBASE-T over their existing structured cabling. What minimum cabling category is required?
- Category 6
- Category 6A
- Category 8.1 (Correct answer)
- Category 5e
Correct answer: Category 8.1
25GBASE-T requires Category 8.1 (or 8.2) cabling, which supports transmission up to 30 meters at 25 Gbps and 40 Gbps.
Question 7: During a site survey for a new network installation, the RCDD discovers the building uses a distributed antenna system (DAS). What primary concern must the RCDD address in the network design?
- DAS antennas must share conduit with structured cabling
- DAS head-end equipment requires dedicated pathways, power, and grounding separate from general IT cabling (Correct answer)
- DAS eliminates the need for horizontal wireless AP cabling
- DAS systems are incompatible with Cat 6A infrastructure
Correct answer: DAS head-end equipment requires dedicated pathways, power, and grounding separate from general IT cabling
DAS head-end equipment has specific space, pathway, power redundancy, and grounding requirements that must be integrated into the overall telecommunications infrastructure design.
RCDD (RCDD): Network Design Principles and Practice 4
A healthcare facility requires in-building wireless coverage for 802.11ax (Wi-Fi 6).
Which cabling infrastructure consideration is most critical for the access point (AP) deployment?