CNT (core networking competencies) EXAM
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ANSWERS AND RATIOALES
Which device is primarily responsible for forwarding packets between different
IP networks?
A. Switch
B. Hub
C. Router
D. Repeater
Rationale: A router operates at the network layer and uses IP addressing and
routing information to determine where packets should be forwarded. A switch
primarily forwards Ethernet frames within a local network based on MAC
addresses, while a hub simply repeats signals to connected ports. A router is
therefore the key device used to connect separate IP networks.
Which OSI model layer is responsible for logical addressing and routing?
A. Physical
B. Data Link
C. Network
D. Transport
Rationale: The Network layer, Layer 3, is responsible for logical addressing and
routing between networks. IPv4 and IPv6 operate at this layer. Routers use Layer 3
information to select paths toward destination networks. The Data Link layer
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,instead handles local frame delivery using technologies such as Ethernet and MAC
addressing.
Which protocol is commonly used to automatically assign IP configuration
information to hosts?
A. DNS
B. DHCP
C. FTP
D. SNMP
Rationale: Dynamic Host Configuration Protocol (DHCP) automatically
provides clients with configuration information such as an IP address, subnet
mask, default gateway, and often DNS server information. This reduces manual
configuration and helps organizations manage addressing efficiently. DNS, by
contrast, primarily resolves names to IP addresses.
What is the primary purpose of a subnet mask in IPv4 networking?
A. To identify the network and host portions of an IPv4 address
B. To encrypt network traffic
C. To translate domain names
D. To identify a device's MAC address
Rationale: An IPv4 subnet mask determines which bits of an IP address
represent the network portion and which represent the host portion. This
information allows devices to determine whether a destination is local or must be
reached through a router. Subnetting also allows networks to be divided into
smaller logical segments.
Which protocol translates a domain name such as example.com into an IP
address?
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,A. ARP
B. DHCP
C. DNS
D. ICMP
Rationale: The Domain Name System (DNS) translates human-readable
domain names into IP addresses and can also provide other types of records. This
allows users and applications to use memorable names rather than numerical
addresses. ARP has a different purpose: resolving an IPv4 address to a MAC
address on a local network.
Which protocol is primarily used to determine the MAC address associated with
an IPv4 address on a local network?
A. ARP
B. DNS
C. BGP
D. DHCP
Rationale: Address Resolution Protocol (ARP) allows an IPv4 host to discover
the Layer 2 MAC address associated with a known IPv4 address on the local
network. The resulting mapping is normally stored temporarily in an ARP cache.
IPv6 does not use ARP; it uses Neighbor Discovery Protocol instead.
Which statement best describes a MAC address?
A. A logical address used for Internet routing
B. A Layer 2 hardware/network-interface identifier used for local frame delivery
C. A DNS hostname
D. A transport-layer port number
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, Rationale: A MAC address is associated with a network interface and is used
by Ethernet networks for Layer 2 communication. Switches commonly use source
MAC addresses to build their forwarding tables and destination MAC addresses to
determine where frames should be sent. IP addresses operate at Layer 3 and are
used for logical network communication.
What happens when a switch receives an Ethernet frame with a destination
MAC address that is not currently in its MAC address table?
A. It automatically drops the frame.
B. It sends the frame only to the router.
C. It floods the frame out appropriate ports within the same VLAN, excluding the
receiving port.
D. It converts the frame into an IP packet.
Rationale: When a switch does not know the destination MAC address, it
treats the frame as an unknown unicast and floods it within the relevant VLAN.
The switch still learns the source MAC address from the frame and associates it
with the receiving port. Once the destination MAC is learned, subsequent frames
can normally be forwarded directly to the appropriate port.
TCP/IP AND PROTOCOLS
Which transport-layer protocol provides reliable, connection-oriented delivery?
A. UDP
B. TCP
C. IP
D. ARP
Rationale: Transmission Control Protocol (TCP) establishes a connection and
provides mechanisms for sequencing, acknowledgments, retransmission, and flow
control. These features help provide reliable delivery. UDP is connectionless and
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PRACTICE | STUDY GUIDE | COMPREHENSIVE
TESTBANK STUDY GUIDE | TESTBANK 2026/2027
UPDATE EXAM QUESTIONS 100% WITH CORRECT
ANSWERS AND RATIOALES
Which device is primarily responsible for forwarding packets between different
IP networks?
A. Switch
B. Hub
C. Router
D. Repeater
Rationale: A router operates at the network layer and uses IP addressing and
routing information to determine where packets should be forwarded. A switch
primarily forwards Ethernet frames within a local network based on MAC
addresses, while a hub simply repeats signals to connected ports. A router is
therefore the key device used to connect separate IP networks.
Which OSI model layer is responsible for logical addressing and routing?
A. Physical
B. Data Link
C. Network
D. Transport
Rationale: The Network layer, Layer 3, is responsible for logical addressing and
routing between networks. IPv4 and IPv6 operate at this layer. Routers use Layer 3
information to select paths toward destination networks. The Data Link layer
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,instead handles local frame delivery using technologies such as Ethernet and MAC
addressing.
Which protocol is commonly used to automatically assign IP configuration
information to hosts?
A. DNS
B. DHCP
C. FTP
D. SNMP
Rationale: Dynamic Host Configuration Protocol (DHCP) automatically
provides clients with configuration information such as an IP address, subnet
mask, default gateway, and often DNS server information. This reduces manual
configuration and helps organizations manage addressing efficiently. DNS, by
contrast, primarily resolves names to IP addresses.
What is the primary purpose of a subnet mask in IPv4 networking?
A. To identify the network and host portions of an IPv4 address
B. To encrypt network traffic
C. To translate domain names
D. To identify a device's MAC address
Rationale: An IPv4 subnet mask determines which bits of an IP address
represent the network portion and which represent the host portion. This
information allows devices to determine whether a destination is local or must be
reached through a router. Subnetting also allows networks to be divided into
smaller logical segments.
Which protocol translates a domain name such as example.com into an IP
address?
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,A. ARP
B. DHCP
C. DNS
D. ICMP
Rationale: The Domain Name System (DNS) translates human-readable
domain names into IP addresses and can also provide other types of records. This
allows users and applications to use memorable names rather than numerical
addresses. ARP has a different purpose: resolving an IPv4 address to a MAC
address on a local network.
Which protocol is primarily used to determine the MAC address associated with
an IPv4 address on a local network?
A. ARP
B. DNS
C. BGP
D. DHCP
Rationale: Address Resolution Protocol (ARP) allows an IPv4 host to discover
the Layer 2 MAC address associated with a known IPv4 address on the local
network. The resulting mapping is normally stored temporarily in an ARP cache.
IPv6 does not use ARP; it uses Neighbor Discovery Protocol instead.
Which statement best describes a MAC address?
A. A logical address used for Internet routing
B. A Layer 2 hardware/network-interface identifier used for local frame delivery
C. A DNS hostname
D. A transport-layer port number
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, Rationale: A MAC address is associated with a network interface and is used
by Ethernet networks for Layer 2 communication. Switches commonly use source
MAC addresses to build their forwarding tables and destination MAC addresses to
determine where frames should be sent. IP addresses operate at Layer 3 and are
used for logical network communication.
What happens when a switch receives an Ethernet frame with a destination
MAC address that is not currently in its MAC address table?
A. It automatically drops the frame.
B. It sends the frame only to the router.
C. It floods the frame out appropriate ports within the same VLAN, excluding the
receiving port.
D. It converts the frame into an IP packet.
Rationale: When a switch does not know the destination MAC address, it
treats the frame as an unknown unicast and floods it within the relevant VLAN.
The switch still learns the source MAC address from the frame and associates it
with the receiving port. Once the destination MAC is learned, subsequent frames
can normally be forwarded directly to the appropriate port.
TCP/IP AND PROTOCOLS
Which transport-layer protocol provides reliable, connection-oriented delivery?
A. UDP
B. TCP
C. IP
D. ARP
Rationale: Transmission Control Protocol (TCP) establishes a connection and
provides mechanisms for sequencing, acknowledgments, retransmission, and flow
control. These features help provide reliable delivery. UDP is connectionless and
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