Cisco CCNA Network Fundamentals Certification Exam | High-
Yield Practice Questions & Detailed Rationales 2026/2027
Question 1
Which OSI model layer is primarily responsible for mechanical,
electrical, and functional specifications for activating, maintaining, and
deactivating physical links between end systems?
A. Physical Layer (Layer 1)
B. Data Link Layer (Layer 2)
C. Network Layer (Layer 3)
D. Transport Layer (Layer 4)
Correct Answer: A. Physical Layer (Layer 1)
Detailed Rationale: Layer 1 (Physical Layer) deals with the physical
medium, voltages, cabling specifications, pinouts, and raw bit
transmission across hardware interfaces.
Question 2
What is the primary function of the TCP/IP Transport Layer?
A. Routing packets across multiple independent internetwork routers.
B. Providing end-to-end logical communication, error control, and
reliability or speed for applications.
C. Translating domain names into numerical IP addresses.
D. Formatting data for presentation to user software interfaces.
,Correct Answer: B. Providing end-to-end logical communication, error
control, and reliability or speed for applications.
Detailed Rationale: The Transport Layer (utilizing protocols like TCP and
UDP) manages end-to-end data delivery, flow control, and reliability
between source and destination hosts.
Question 3
What is the maximum recommended cable length for standard
Category 5e or Category 6 Unshielded Twisted Pair (UTP) copper cabling
in an Ethernet LAN?
A. 50 meters
B. 100 meters
C. 500 meters
D. 1000 meters
Correct Answer: B. 100 meters
Detailed Rationale: Standard TIA/EIA-568 guidelines specify a
maximum distance of 100 meters (90 meters of permanent link plus 27
feet/approx. 10 meters of patch cords) for UTP copper Ethernet cabling.
Question 4
Why are crossover Ethernet cables generally no longer required when
connecting two modern switches or routers directly together?
A. Modern devices utilize fiber optic transceivers exclusively.
B. Modern Ethernet interfaces support Auto-MDIX (Medium Dependent
Interface Crossover), which dynamically detects and corrects wire
pinout configurations.
,C. Ethernet frames automatically correct wire reversals at Layer 2.
D. Standard UTP cables eliminate signal cross-talk internally.
Correct Answer: B. Modern devices utilize Auto-MDIX (Medium
Dependent Interface Crossover), which dynamically detects and
corrects wire pinout configurations.
Question 5
According to RFC 1918, which of the following blocks represents private
IPv4 address space?
A. 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
B. 192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24
C. 169.254.0.0/16
D. 224.0.0.0/4
Correct Answer: A. 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
Detailed Rationale: RFC 1918 defines private IPv4 address ranges that
are non-routable on the public internet, allowing organizations to reuse
addresses internally.
Question 6
An administrator has been given the subnet mask 255.255.255.192.
How many usable host IP addresses are available in this subnet?
A. 30 usable hosts
B. 62 usable hosts
C. 126 usable hosts
D. 254 usable hosts
, Correct Answer: B. 62 usable hosts
Detailed Rationale: A subnet mask of 255.255.255.192 corresponds to
a /26 prefix, leaving 6 bits for host addressing (26 − 2 = 62 usable
hosts).
Question 7
What is the purpose of the Time-to-Live (TTL) field in an IPv4 packet
header?
A. To specify the maximum payload length in bytes.
B. To prevent packets from circulating indefinitely in routing loops by
decrementing the value at each router hop.
C. To encrypt session keys for secure transmission.
D. To indicate the packet's priority for Quality of Service (QoS).
Correct Answer: B. To prevent packets from circulating indefinitely in
routing loops by decrementing the value at each router hop.
Question 8
What key operational difference distinguishes TCP from UDP?
A. TCP is connection-oriented and provides reliable, ordered delivery
with error recovery, whereas UDP is connectionless and lightweight
with no delivery guarantees.
B. TCP uses broadcast addressing, while UDP uses unicast addressing.
C. TCP operates at Layer 2, while UDP operates at Layer 7.
D. There is no difference; they share identical packet structures.
Yield Practice Questions & Detailed Rationales 2026/2027
Question 1
Which OSI model layer is primarily responsible for mechanical,
electrical, and functional specifications for activating, maintaining, and
deactivating physical links between end systems?
A. Physical Layer (Layer 1)
B. Data Link Layer (Layer 2)
C. Network Layer (Layer 3)
D. Transport Layer (Layer 4)
Correct Answer: A. Physical Layer (Layer 1)
Detailed Rationale: Layer 1 (Physical Layer) deals with the physical
medium, voltages, cabling specifications, pinouts, and raw bit
transmission across hardware interfaces.
Question 2
What is the primary function of the TCP/IP Transport Layer?
A. Routing packets across multiple independent internetwork routers.
B. Providing end-to-end logical communication, error control, and
reliability or speed for applications.
C. Translating domain names into numerical IP addresses.
D. Formatting data for presentation to user software interfaces.
,Correct Answer: B. Providing end-to-end logical communication, error
control, and reliability or speed for applications.
Detailed Rationale: The Transport Layer (utilizing protocols like TCP and
UDP) manages end-to-end data delivery, flow control, and reliability
between source and destination hosts.
Question 3
What is the maximum recommended cable length for standard
Category 5e or Category 6 Unshielded Twisted Pair (UTP) copper cabling
in an Ethernet LAN?
A. 50 meters
B. 100 meters
C. 500 meters
D. 1000 meters
Correct Answer: B. 100 meters
Detailed Rationale: Standard TIA/EIA-568 guidelines specify a
maximum distance of 100 meters (90 meters of permanent link plus 27
feet/approx. 10 meters of patch cords) for UTP copper Ethernet cabling.
Question 4
Why are crossover Ethernet cables generally no longer required when
connecting two modern switches or routers directly together?
A. Modern devices utilize fiber optic transceivers exclusively.
B. Modern Ethernet interfaces support Auto-MDIX (Medium Dependent
Interface Crossover), which dynamically detects and corrects wire
pinout configurations.
,C. Ethernet frames automatically correct wire reversals at Layer 2.
D. Standard UTP cables eliminate signal cross-talk internally.
Correct Answer: B. Modern devices utilize Auto-MDIX (Medium
Dependent Interface Crossover), which dynamically detects and
corrects wire pinout configurations.
Question 5
According to RFC 1918, which of the following blocks represents private
IPv4 address space?
A. 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
B. 192.0.2.0/24, 198.51.100.0/24, 203.0.113.0/24
C. 169.254.0.0/16
D. 224.0.0.0/4
Correct Answer: A. 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16
Detailed Rationale: RFC 1918 defines private IPv4 address ranges that
are non-routable on the public internet, allowing organizations to reuse
addresses internally.
Question 6
An administrator has been given the subnet mask 255.255.255.192.
How many usable host IP addresses are available in this subnet?
A. 30 usable hosts
B. 62 usable hosts
C. 126 usable hosts
D. 254 usable hosts
, Correct Answer: B. 62 usable hosts
Detailed Rationale: A subnet mask of 255.255.255.192 corresponds to
a /26 prefix, leaving 6 bits for host addressing (26 − 2 = 62 usable
hosts).
Question 7
What is the purpose of the Time-to-Live (TTL) field in an IPv4 packet
header?
A. To specify the maximum payload length in bytes.
B. To prevent packets from circulating indefinitely in routing loops by
decrementing the value at each router hop.
C. To encrypt session keys for secure transmission.
D. To indicate the packet's priority for Quality of Service (QoS).
Correct Answer: B. To prevent packets from circulating indefinitely in
routing loops by decrementing the value at each router hop.
Question 8
What key operational difference distinguishes TCP from UDP?
A. TCP is connection-oriented and provides reliable, ordered delivery
with error recovery, whereas UDP is connectionless and lightweight
with no delivery guarantees.
B. TCP uses broadcast addressing, while UDP uses unicast addressing.
C. TCP operates at Layer 2, while UDP operates at Layer 7.
D. There is no difference; they share identical packet structures.
