CNT (core networking competencies) EXAM
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ANSWERS AND RATIOALES
Which layer of the OSI model is primarily responsible for logical addressing and
routing packets between different networks?
A. Physical layer
B. Data Link layer
C. Network layer
D. Session layer
✓ Correct Answer: C. Network layer
Rationale: The Network layer, Layer 3 of the OSI model, is responsible for
logical addressing and determining how packets travel between networks. IPv4
and IPv6 operate primarily at this layer. Routers use Layer 3 addressing
information to determine the appropriate path for forwarding packets toward
their destination. The Data Link layer, by comparison, handles local frame delivery,
while the Physical layer deals with the transmission of raw bits across a physical
medium.
Which protocol is primarily responsible for translating a domain name such as
example.com into an IP address?
A. DHCP
B. DNS
C. FTP
D. ARP
✓ Correct Answer: B. DNS
Page 1 of 68
, Rationale: The Domain Name System (DNS) translates human-readable
domain names into IP addresses and performs other name-resolution functions.
This allows users and applications to access services using meaningful names
rather than remembering numerical IP addresses. DHCP has a different role: it
dynamically provides configuration information such as IP addresses, subnet
masks, gateways, and DNS server addresses to clients.
What is the primary purpose of DHCP on an IP network?
A. Encrypting network traffic
B. Automatically providing network configuration information to clients
C. Translating private addresses into public addresses
D. Routing packets between autonomous systems
✓ Correct Answer: B. Automatically providing network configuration
information to clients
Rationale: Dynamic Host Configuration Protocol (DHCP) allows network
devices to automatically receive configuration information. Depending on the
network, this can include an IP address, subnet mask, default gateway, DNS
servers, lease duration, and other options. DHCP reduces the amount of manual
configuration required and helps prevent duplicate IP addressing caused by
assigning addresses individually without centralized coordination.
Which device normally operates primarily at Layer 2 of the OSI model?
A. Ethernet switch
B. Router
C. DNS server
D. Application gateway
✓ Correct Answer: A. Ethernet switch
Rationale: A traditional Ethernet switch primarily operates at the Data Link
layer, Layer 2. It examines MAC addresses in Ethernet frames and uses its MAC
address table to determine which switch port should receive a frame. Some
Page 2 of 68
,modern switches also contain Layer 3 routing capabilities, but their fundamental
switching function is associated with Layer 2.
What information does an Ethernet switch primarily use to make a Layer 2
forwarding decision?
A. Destination MAC address
B. Destination DNS name
C. TCP port number
D. HTTP header
✓ Correct Answer: A. Destination MAC address
Rationale: An Ethernet switch examines the destination MAC address of an
incoming frame and consults its MAC address table to determine where to
forward that frame. The switch learns MAC addresses by observing the source
MAC addresses of frames received on its ports. This process allows the switch to
forward frames efficiently rather than sending every frame out every port.
What is the primary function of a router?
A. Forwarding traffic between different IP networks
B. Converting digital signals into analog telephone signals
C. Assigning MAC addresses to Ethernet interfaces
D. Storing web pages for clients
✓ Correct Answer: A. Forwarding traffic between different IP networks
Rationale: Routers connect separate IP networks and make forwarding
decisions based on Layer 3 addressing information. A router examines the
destination IP address and consults its routing table to determine an appropriate
next hop or outgoing interface. This distinguishes routing from switching, where
Layer 2 frames are generally forwarded within a local network or VLAN.
Which protocol is used to discover the MAC address associated with an IPv4
address on a local network?
Page 3 of 68
, A. DNS
B. ARP
C. DHCP
D. ICMP
✓ Correct Answer: B. ARP
Rationale: Address Resolution Protocol (ARP) maps an IPv4 address to a MAC
address on a local network. When a device knows the destination IPv4 address
but needs the corresponding Ethernet MAC address, it can send an ARP request.
The device using that IP address can respond with its MAC address, allowing the
sender to construct the Ethernet frame needed for local delivery.
What is the purpose of ICMP?
A. Providing network diagnostic and control messaging
B. Assigning IP addresses automatically
C. Encrypting Ethernet frames
D. Resolving domain names
✓ Correct Answer: A. Providing network diagnostic and control messaging
Rationale: Internet Control Message Protocol (ICMP) is used for network-layer
diagnostic, error-reporting, and control functions. Utilities such as ping commonly
use ICMP Echo Request and Echo Reply messages to test reachability. ICMP can
also communicate certain network conditions, although filtering ICMP can affect
diagnostic capabilities and some network functions.
Which command is commonly used to test basic IP connectivity to another host?
A. ping
B. format
C. mkdir
D. hostname
✓ Correct Answer: A. ping
Page 4 of 68
PRACTICE | STUDY GUIDE | COMPREHENSIVE
TESTBANK STUDY GUIDE | TESTBANK 2026/2027
UPDATE EXAM QUESTIONS 100% WITH CORRECT
ANSWERS AND RATIOALES
Which layer of the OSI model is primarily responsible for logical addressing and
routing packets between different networks?
A. Physical layer
B. Data Link layer
C. Network layer
D. Session layer
✓ Correct Answer: C. Network layer
Rationale: The Network layer, Layer 3 of the OSI model, is responsible for
logical addressing and determining how packets travel between networks. IPv4
and IPv6 operate primarily at this layer. Routers use Layer 3 addressing
information to determine the appropriate path for forwarding packets toward
their destination. The Data Link layer, by comparison, handles local frame delivery,
while the Physical layer deals with the transmission of raw bits across a physical
medium.
Which protocol is primarily responsible for translating a domain name such as
example.com into an IP address?
A. DHCP
B. DNS
C. FTP
D. ARP
✓ Correct Answer: B. DNS
Page 1 of 68
, Rationale: The Domain Name System (DNS) translates human-readable
domain names into IP addresses and performs other name-resolution functions.
This allows users and applications to access services using meaningful names
rather than remembering numerical IP addresses. DHCP has a different role: it
dynamically provides configuration information such as IP addresses, subnet
masks, gateways, and DNS server addresses to clients.
What is the primary purpose of DHCP on an IP network?
A. Encrypting network traffic
B. Automatically providing network configuration information to clients
C. Translating private addresses into public addresses
D. Routing packets between autonomous systems
✓ Correct Answer: B. Automatically providing network configuration
information to clients
Rationale: Dynamic Host Configuration Protocol (DHCP) allows network
devices to automatically receive configuration information. Depending on the
network, this can include an IP address, subnet mask, default gateway, DNS
servers, lease duration, and other options. DHCP reduces the amount of manual
configuration required and helps prevent duplicate IP addressing caused by
assigning addresses individually without centralized coordination.
Which device normally operates primarily at Layer 2 of the OSI model?
A. Ethernet switch
B. Router
C. DNS server
D. Application gateway
✓ Correct Answer: A. Ethernet switch
Rationale: A traditional Ethernet switch primarily operates at the Data Link
layer, Layer 2. It examines MAC addresses in Ethernet frames and uses its MAC
address table to determine which switch port should receive a frame. Some
Page 2 of 68
,modern switches also contain Layer 3 routing capabilities, but their fundamental
switching function is associated with Layer 2.
What information does an Ethernet switch primarily use to make a Layer 2
forwarding decision?
A. Destination MAC address
B. Destination DNS name
C. TCP port number
D. HTTP header
✓ Correct Answer: A. Destination MAC address
Rationale: An Ethernet switch examines the destination MAC address of an
incoming frame and consults its MAC address table to determine where to
forward that frame. The switch learns MAC addresses by observing the source
MAC addresses of frames received on its ports. This process allows the switch to
forward frames efficiently rather than sending every frame out every port.
What is the primary function of a router?
A. Forwarding traffic between different IP networks
B. Converting digital signals into analog telephone signals
C. Assigning MAC addresses to Ethernet interfaces
D. Storing web pages for clients
✓ Correct Answer: A. Forwarding traffic between different IP networks
Rationale: Routers connect separate IP networks and make forwarding
decisions based on Layer 3 addressing information. A router examines the
destination IP address and consults its routing table to determine an appropriate
next hop or outgoing interface. This distinguishes routing from switching, where
Layer 2 frames are generally forwarded within a local network or VLAN.
Which protocol is used to discover the MAC address associated with an IPv4
address on a local network?
Page 3 of 68
, A. DNS
B. ARP
C. DHCP
D. ICMP
✓ Correct Answer: B. ARP
Rationale: Address Resolution Protocol (ARP) maps an IPv4 address to a MAC
address on a local network. When a device knows the destination IPv4 address
but needs the corresponding Ethernet MAC address, it can send an ARP request.
The device using that IP address can respond with its MAC address, allowing the
sender to construct the Ethernet frame needed for local delivery.
What is the purpose of ICMP?
A. Providing network diagnostic and control messaging
B. Assigning IP addresses automatically
C. Encrypting Ethernet frames
D. Resolving domain names
✓ Correct Answer: A. Providing network diagnostic and control messaging
Rationale: Internet Control Message Protocol (ICMP) is used for network-layer
diagnostic, error-reporting, and control functions. Utilities such as ping commonly
use ICMP Echo Request and Echo Reply messages to test reachability. ICMP can
also communicate certain network conditions, although filtering ICMP can affect
diagnostic capabilities and some network functions.
Which command is commonly used to test basic IP connectivity to another host?
A. ping
B. format
C. mkdir
D. hostname
✓ Correct Answer: A. ping
Page 4 of 68
