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Engineer Information Communications practice questions

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Question 1Information and Communication Systems

In the IPv4 header, which field is decremented by each router that forwards a packet and prevents endless looping?

  1. Identification
  2. Time to Live (TTL) Correct answer.
  3. Header Checksum
  4. Total Length

Explanation

The TTL field is set by the sender and reduced by one at every router that forwards the datagram. When it reaches zero the packet is discarded and an ICMP Time Exceeded message is returned, which stops packets from circulating forever. This mechanism is also the basis of traceroute probing.

Question 2Information and Communication Systems

A host is configured with IPv4 address 192.168.10.130 and subnet mask 255.255.255.192. Which address is the directed broadcast address of its subnet?

  1. 192.168.10.128
  2. 192.168.10.255
  3. 192.168.10.191 Correct answer.
  4. 192.168.10.129

Explanation

A /26 mask leaves 6 host bits, so subnets step in blocks of 64. The address 192.168.10.130 falls in the block 192.168.10.128 through 192.168.10.191, and the broadcast address is the last address of that block.

Question 3Information and Communication Systems

Which statement describes the main purpose of the Address Resolution Protocol (ARP) on an Ethernet LAN?

  1. It maps a known IPv4 address to the corresponding MAC address. Correct answer.
  2. It distributes default gateway information to hosts automatically.
  3. It maps a known MAC address to the corresponding IPv4 address.
  4. It translates private IPv4 addresses into public addresses.

Explanation

ARP broadcasts a request asking which station owns a given IPv4 address, and the owner replies with its MAC address so the frame can be encapsulated. The reverse lookup, from MAC to IP, is the job of RARP or DHCP-style mechanisms rather than ARP.

Question 4Information and Communication Systems

A TCP sender uses a congestion window of 8 MSS and a receiver-advertised window of 5 MSS, with no other constraints. How much unacknowledged data can it have in flight at most?

  1. 5 MSS Correct answer.
  2. 13 MSS
  3. 8 MSS
  4. 40 MSS

Explanation

The effective send window is the minimum of the congestion window and the receiver's advertised window. Here the receiver window of 5 MSS is smaller, so it limits the amount of unacknowledged data to 5 MSS.

Question 5Information and Communication Systems

During the TCP three-way handshake, which flag combination is carried by the second segment sent by the server?

  1. FIN and ACK
  2. SYN and ACK Correct answer.
  3. SYN only
  4. ACK only

Explanation

The server answers the client's initial SYN with a segment that both acknowledges the client's sequence number and carries its own initial sequence number. That segment therefore has the SYN and ACK flags set simultaneously. The third segment then completes the handshake with ACK only.

Question 6Information and Communication Systems

Which DNS record type should be queried to obtain the mail servers responsible for accepting e-mail for a domain?

  1. PTR
  2. A
  3. CNAME
  4. MX Correct answer.

Explanation

MX records list the mail exchange hosts for a domain together with a preference value used to order them. Senders consult these records to decide where to deliver SMTP mail.

Question 7Information and Communication Systems

A route summarization design must cover the prefixes 172.16.0.0/24 through 172.16.7.0/24. Which single summary prefix is the most specific that includes all of them?

  1. 172.16.0.0/19
  2. 172.16.0.0/22
  3. 172.16.0.0/20
  4. 172.16.0.0/21 Correct answer.

Explanation

Eight consecutive /24 networks span addresses 172.16.0.0 to 172.16.7.255, which is a block of 2048 addresses. That block is exactly a /21, since 32 minus 5 host bits gives 3 network bits added to the /16 base. A /21 is therefore the most specific single prefix covering all eight subnets.

Question 8Information and Communication Systems

Which protocol provides loop-free Layer 2 forwarding by computing a single active topology and blocking redundant links?

  1. Link Aggregation Control Protocol
  2. Dynamic Host Configuration Protocol
  3. VLAN Trunking Protocol
  4. Spanning Tree Protocol Correct answer.

Explanation

Spanning Tree Protocol elects a root bridge and places redundant ports in a blocking state so that only one active path exists between any two points. This prevents broadcast storms caused by Layer 2 loops.

Question 9Information and Communication Systems

An Ethernet frame arrives at a switch port whose source MAC address is not yet in the MAC address table. What does the switch do with the frame's source entry and its forwarding decision?

  1. It sends the frame back out of the receiving port.
  2. It floods the frame and does not learn the source.
  3. It learns the source address on the receiving port and forwards the frame only toward the destination if known. Correct answer.
  4. It discards the frame until the address table is refreshed.

Explanation

A switch always learns the source MAC address and associates it with the ingress port, refreshing the aging timer. For forwarding, it looks up the destination: if the destination is known, the frame goes out that port only; if unknown, it is flooded to all ports in the VLAN except the ingress port.

Question 10Information and Communication Systems

Which statement about CSMA/CD in classic shared-medium Ethernet is correct?

  1. A station may transmit immediately whenever the medium is idle after sensing it.
  2. Stations use a fixed time slot assigned by a central controller.
  3. A station defers transmission while the medium is busy and starts only after the medium becomes idle. Correct answer.
  4. Collisions cannot occur because stations take turns using a token.

Explanation

Carrier sense means a station listens before transmitting and waits while the medium is occupied. Once the medium is idle it begins transmission, and if a collision is detected it stops and retries after a random backoff.

Question 11Information and Communication Systems

In IEEE 802.11 wireless LANs, what is the main role of the RTS/CTS exchange?

  1. To encrypt management frames between the station and the access point.
  2. To authenticate a station against a RADIUS server.
  3. To reserve the medium and reduce collisions caused by hidden terminals. Correct answer.
  4. To negotiate the channel bandwidth used for the association.

Explanation

A station sends a Request to Send and waits for a Clear to Send before transmitting data. Neighboring stations that hear either frame defer for the reserved duration, which mitigates the hidden-node problem and reduces collisions.

Question 12Information and Communication Systems

A network uses CIDR and a router receives the routes 10.1.0.0/16, 10.1.4.0/24, and 10.1.4.0/22. Which route matches a packet addressed to 10.1.4.77 under longest-prefix-match?

  1. 10.1.0.0/16
  2. A default route 0.0.0.0/0
  3. 10.1.4.0/24 Correct answer.
  4. 10.1.4.0/22

Explanation

Longest-prefix-match selects the route with the most specific mask among those that contain the destination. All three listed prefixes cover 10.1.4.77, but /24 has more network bits than /16 or /22. A default route is only used when no more specific route exists.

Question 13Information and Communication Systems

Which QoS mechanism classifies packets by inspecting fields such as source address, destination address, and TCP/UDP port numbers?

  1. Packet classification with ACLs Correct answer.
  2. Traffic shaping
  3. Traffic policing
  4. Weighted random early detection

Explanation

Classification examines packet header fields, often with access control lists, to assign packets to classes before they are marked or queued. Policing, shaping, and queue management act on traffic after classification has occurred.

Question 14Information and Communication Systems

A company wants to connect two branch sites over a public network with confidentiality and integrity while avoiding dedicated leased lines. Which technology best fits this requirement?

  1. A Layer 2 transparent bridge over the Internet
  2. A public web proxy
  3. A hub-and-spoke topology using unencrypted GRE only
  4. An IPsec VPN tunnel Correct answer.

Explanation

IPsec provides authentication, integrity protection, and encryption at the IP layer, which allows secure communication over untrusted networks without dedicated circuits. GRE alone carries traffic but provides no confidentiality.

Question 15Information and Communication Systems

Which statement correctly describes the difference between the TCP and UDP transport protocols?

  1. TCP is connectionless and fast, while UDP guarantees in-order delivery.
  2. UDP performs retransmission of lost segments while TCP does not.
  3. Both protocols guarantee delivery and differ only in header size.
  4. TCP provides connection-oriented, reliable delivery with flow control, while UDP is connectionless and unreliable. Correct answer.

Explanation

TCP establishes a connection, numbers segments, acknowledges data, retransmits losses, and applies flow and congestion control. UDP sends datagrams without connection setup or delivery guarantees, which suits real-time and query-response traffic.

Question 16Information and Communication Systems

Which mechanism does DHCP use to prevent a client from keeping an assigned address indefinitely?

  1. Lease time with renewal via DHCPREQUEST Correct answer.
  2. Static ARP binding
  3. Router advertisement suppression
  4. Reverse DNS lookup

Explanation

DHCP assigns addresses for a bounded lease period. The client renews before expiry, typically by unicast DHCPREQUEST at half the lease time, and the server may extend or refuse the lease.

Question 17Information and Communication Systems

In a network design, which is the primary advantage of deploying a routed core instead of a large flat Layer 2 domain?

  1. It guarantees encryption of all user traffic.
  2. It bounds broadcast domains and improves convergence and stability. Correct answer.
  3. It eliminates the need for IP addressing.
  4. It removes the need for routing protocols.

Explanation

A Layer 3 core limits broadcast propagation to each subnet and allows routing protocols to converge around failures without relying on spanning tree. This reduces the blast radius of loops and improves stability.

Question 18Information and Communication Systems

A link has a bandwidth of 10 Mbps and a one-way propagation delay of 20 ms. Ignoring processing and queuing, what is the approximate round-trip time for a small packet?

  1. 2 ms
  2. 40 ms Correct answer.
  3. 200 ms
  4. 20 ms

Explanation

Round-trip time is twice the one-way propagation delay for a small packet whose transmission time is negligible. Two times 20 ms gives 40 ms. Transmission delay at 10 Mbps for a small packet is on the order of microseconds and can be ignored.

Question 19Information and Communication Systems

Which statement about the OSI reference model layers is correct?

  1. The data link layer provides end-to-end reliable delivery between hosts.
  2. The session layer performs bit-level error detection on the wire.
  3. The transport layer defines the physical signaling and connector pinouts.
  4. The network layer provides logical addressing and routing between networks. Correct answer.

Explanation

The network layer handles logical addressing and path selection so that packets can travel between different networks. End-to-end reliability belongs to the transport layer, and physical signaling belongs to the physical layer.

Question 20Information and Communication Systems

In optical fiber transmission, which property primarily limits the maximum distance for a given data rate in multimode fiber?

  1. Chromatic absorption by the cladding
  2. Fresnel reflection at the connector
  3. Modal dispersion Correct answer.
  4. Polarization rotation

Explanation

Different modes travel different path lengths through a multimode fiber, so pulses spread in time and adjacent symbols overlap as distance grows. This modal dispersion limits the bandwidth-distance product, which is why single-mode fiber is used for long links.

Question 21Information and Communication Systems

Which modulation scheme carries two bits per symbol and is widely used in digital microwave links?

  1. QPSK Correct answer.
  2. 16QAM
  3. BPSK
  4. 8PSK

Explanation

QPSK uses four phase states, and log2(4) equals two bits per symbol. BPSK carries one bit, while 8PSK and 16QAM carry three and four bits per symbol respectively.

Question 22Information and Communication Systems

A radio link experiences a multipath delay spread of 5 microseconds. Which statement is correct about the symbol period needed to avoid significant intersymbol interference?

  1. The symbol period is unrelated to delay spread.
  2. The symbol period should be much smaller than 5 microseconds.
  3. The symbol period should be much larger than 5 microseconds. Correct answer.
  4. The symbol period must equal exactly 5 microseconds.

Explanation

When the symbol period is comparable to or shorter than the delay spread, delayed echoes arrive within the same or adjacent symbol intervals and cause intersymbol interference. Keeping the symbol period much longer than the delay spread, or adding a guard interval such as a cyclic prefix, mitigates this.

Question 23Information and Communication Systems

Which statement about the Nyquist sampling theorem in a digital communication receiver is correct?

  1. Sampling must occur at exactly the highest frequency component.
  2. Sampling rate has no effect on reconstruction fidelity.
  3. Sampling must occur at half the highest frequency component.
  4. Sampling must occur at least twice the highest frequency component of the signal. Correct answer.

Explanation

The Nyquist criterion requires a sampling rate of at least twice the highest frequency present in the band-limited signal. Sampling below that rate causes aliasing, where high-frequency components fold into lower frequencies and cannot be separated.

Question 24Information and Communication Systems

A fiber link budget allows 20 dB of total loss. The fiber has 0.35 dB/km attenuation and there are two connectors at 0.5 dB each plus two splices at 0.1 dB each. What is the approximate maximum fiber length?

  1. About 60 km
  2. About 53 km Correct answer.
  3. About 65 km
  4. About 57 km

Explanation

Connector and splice losses total 1.0 dB plus 0.2 dB, or 1.2 dB, leaving 18.8 dB for the fiber. Dividing 18.8 dB by 0.35 dB/km gives approximately 53.7 km, so about 53 km is the closest answer.

Question 25Information and Communication Systems

Which characteristic distinguishes synchronous optical network (SONET/SDH) transport from plesiochronous digital hierarchy (PDH) transport?

  1. SONET/SDH carries only packet traffic and cannot transport voice circuits.
  2. SONET/SDH relies on bit stuffing at every multiplexing stage, as PDH does.
  3. SONET/SDH uses a single global reference clock and byte-interleaved multiplexing, enabling direct access to tributaries. Correct answer.
  4. SONET/SDH operates only over copper pairs and cannot use optical fiber.

Explanation

SONET/SDH networks are synchronized to a common reference and multiplex tributaries byte by byte, so individual channels can be dropped and inserted without demultiplexing the entire hierarchy. PDH instead uses bit stuffing at each level, which complicates access to lower-rate signals.

Question 26Information and Communication Systems

A network engineer is designing an IP address plan for a new office with 500 hosts on a single subnet. Which prefix length provides enough usable host addresses while minimizing address waste?

  1. /24
  2. /22
  3. /23 Correct answer.
  4. /25

Explanation

A /23 prefix provides 2^(32-23) = 512 total addresses, and after reserving the network and broadcast addresses, 510 usable host addresses, which meets the requirement of 500 hosts with minimal waste. A /24 provides only 254 usable addresses, which is insufficient, while a /22 provides 1022 usable addresses, which wastes more than necessary.

Question 27Information and Communication Systems

Which statement best describes the function of the Address Resolution Protocol (ARP) in an IPv4 network?

  1. It resolves domain names to IPv4 addresses for client applications.
  2. It translates private IPv4 addresses to public IPv4 addresses for Internet access.
  3. It assigns a dynamic IPv4 address to a host from a central server pool.
  4. It maps a known IPv4 address to the corresponding MAC address on the local link. Correct answer.

Explanation

ARP operates on the local broadcast domain to discover the MAC address associated with a given IPv4 address, allowing frames to be encapsulated with the correct destination link-layer address. It does not perform address assignment, NAT, or DNS resolution, which are handled by DHCP, NAT, and DNS respectively.

Question 28Information and Communication Systems

In a TCP connection, the sender has a congestion window (cwnd) of 4 MSS and the receiver advertises a window (rwnd) of 8 MSS. What is the maximum amount of unacknowledged data the sender may have in flight?

  1. 4 MSS Correct answer.
  2. 12 MSS
  3. 2 MSS
  4. 8 MSS

Explanation

TCP flow control and congestion control both limit the sender: the effective window is the minimum of the congestion window and the receiver's advertised window. Here min(4 MSS, 8 MSS) = 4 MSS, so the sender may have at most 4 MSS of unacknowledged data in flight.

Question 29Information and Communication Systems

Which mechanism allows an IP packet to be fragmented and reassembled correctly when it traverses links with different MTUs?

  1. The Time-to-Live field decremented at each router.
  2. The Type of Service field used for QoS marking.
  3. The Header Checksum field recomputed at every hop.
  4. The Identification, Flags, and Fragment Offset fields in the IPv4 header. Correct answer.

Explanation

IPv4 fragmentation uses the Identification field to group fragments of the same original datagram, the Flags field (MF and DF bits) to indicate more fragments or prohibit fragmentation, and the Fragment Offset field to place each fragment correctly during reassembly. The TTL, ToS, and Header Checksum fields serve different purposes and do not support fragmentation.

Question 30Information and Communication Systems

A network administrator needs to allow Secure Shell (SSH) access from the Internet to a server with private address 192.168.1.10. Which configuration on the border router accomplishes this with a single public address?

  1. PAT using the overload keyword without a static entry.
  2. Dynamic NAT with a pool of public addresses.
  3. A routing protocol advertisement of the private address.
  4. Static NAT mapping TCP port 22 on the public interface to port 22 on 192.168.1.10. Correct answer.

Explanation

Port forwarding via static NAT (sometimes called a static PAT entry) maps a specific TCP port on the public address to the same port on the internal server, allowing inbound SSH connections. Dynamic NAT and PAT overload without a static entry do not permit unsolicited inbound connections, and advertising a private address on the Internet is not viable.

Question 31Information and Communication Systems

Which statement about the DiffServ (Differentiated Services) architecture is correct?

  1. It classifies packets into behavior aggregates using the DSCP field and applies per-hop behaviors. Correct answer.
  2. It requires all routers to maintain per-flow state for each microflow.
  3. It reserves end-to-end bandwidth for each flow using RSVP signaling.
  4. It guarantees strict priority for all voice traffic by default.

Explanation

DiffServ uses the 6-bit DSCP in the IP header to mark packets into behavior aggregates, and routers apply per-hop behaviors (such as expedited forwarding or assured forwarding) to these aggregates without maintaining per-flow state. RSVP-based reservation is characteristic of IntServ, not DiffServ.

Question 32Information and Communication Systems

Which interior gateway protocol uses a two-level hierarchy with areas and a designated router election on multi-access networks to reduce adjacency and flooding overhead?

  1. OSPF Correct answer.
  2. EIGRP
  3. BGP
  4. RIP version 2

Explanation

OSPF supports a two-level hierarchy of areas (backbone area 0 and other areas) and elects a designated router and backup designated router on multi-access segments to limit the number of adjacencies and control flooding. RIP is a distance-vector protocol without areas, EIGRP uses autonomous systems and feasible successors but not OSPF-style areas, and BGP is an exterior gateway protocol.

Question 33Information and Communication Systems

A router receives a packet destined for 192.168.10.5. Its routing table contains the entries 192.168.10.0/24 via next-hop A, 192.168.0.0/16 via next-hop B, and 0.0.0.0/0 via next-hop C. Which next-hop is used?

  1. The packet is dropped
  2. Next-hop C
  3. Next-hop A Correct answer.
  4. Next-hop B

Explanation

When multiple routes match a destination, a router selects the one with the longest prefix match. The /24 route matches the destination and is more specific than the /16 and the default route, so next-hop A is chosen.

Question 34Information and Communication Systems

Which security property is provided by the IPsec Authentication Header (AH) but not by the Encapsulating Security Payload (ESP) when ESP is used without authentication?

  1. Data origin authentication and integrity protection for the IP header. Correct answer.
  2. Protection against replay attacks.
  3. Confidentiality of the packet payload.
  4. Encryption of the IP header.

Explanation

AH provides integrity and data origin authentication for the entire IP packet, including the outer IP header, whereas ESP without authentication provides only confidentiality. ESP can provide authentication and anti-replay when configured, but those are not inherent to ESP without authentication.

Question 35Information and Communication Systems

In a network using Rapid Spanning Tree Protocol (RSTP), which port role is assigned to a port that provides an alternate path to the root bridge and can transition to forwarding without waiting for timer expiry if the root port fails?

  1. Alternate port Correct answer.
  2. Root port
  3. Backup port
  4. Designated port

Explanation

In RSTP, an alternate port is a discarding port that receives superior BPDUs from another bridge and offers an alternative path toward the root bridge; it can become the root port quickly upon failure. A backup port provides a backup path to the same segment, a designated port forwards on a segment, and a root port is the best path to the root.

Question 36Information and Communication Systems

Which statement about the use of private IPv4 address space defined in RFC 1918 is correct?

  1. Private addresses are assigned by IANA to organizations for global routing.
  2. Private addresses can be used on the Internet if all routers agree to forward them.
  3. Private addresses are a subset of multicast addresses used for group communication.
  4. Private addresses are not globally routable and require NAT for Internet connectivity. Correct answer.

Explanation

RFC 1918 defines blocks such as 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16 for use within private networks; these addresses are not allocated globally and therefore must be translated by NAT to reach the Internet. They are not assigned for global routing, cannot be routed on the public Internet, and are distinct from multicast addresses.

Question 37Information and Communication Systems

Which technology allows a service provider to carry multiple customer VLANs across a shared backbone while maintaining isolation between customers?

  1. 802.1X port-based authentication
  2. Link aggregation (802.3ad)
  3. Storm control
  4. QinQ (802.1ad) VLAN stacking Correct answer.

Explanation

QinQ, standardized as IEEE 802.1ad, adds an outer service-provider VLAN tag to customer frames so that each customer's VLANs remain isolated while traversing the provider backbone. 802.1X provides access control, link aggregation bundles links for bandwidth and redundancy, and storm control limits broadcast or multicast floods.

Question 38Information and Communication Systems

A network engineer observes that OSPF neighbor adjacencies fail to form between two routers on the same Ethernet segment. Which configuration mismatch is a likely cause?

  1. The OSPF network types are both broadcast.
  2. The OSPF hello and dead intervals differ between the interfaces. Correct answer.
  3. The interface MTU values are identical.
  4. The OSPF router IDs are identical.

Explanation

For OSPF neighbors to become adjacent, several interface parameters must match, including the hello and dead intervals, area ID, authentication, and stub area flags. A mismatch in hello or dead timers prevents adjacency formation, whereas identical router IDs, MTUs, and network types do not cause failure.

Question 39Information and Communication Systems

Which statement about the use of jumbo frames in an Ethernet network is correct?

  1. All devices on the path, including switches and routers, must support and be configured for the larger MTU. Correct answer.
  2. Jumbo frames reduce the maximum transmission unit (MTU) to lower latency.
  3. Jumbo frames are defined in IEEE 802.3 standard with a fixed 9000-byte payload.
  4. Jumbo frames increase the frame check sequence (FCS) length to improve error detection.

Explanation

Jumbo frames exceed the standard 1500-byte payload and require consistent configuration of a larger MTU on every device along the path; otherwise, frames may be dropped. The FCS length remains 32 bits, jumbo frames increase rather than decrease MTU, and there is no single IEEE standard fixing the payload size.

Question 40Information and Communication Systems

Which protocol provides loop prevention in a Layer 3 network by using a topology table and feasible successor routes?

  1. OSPF
  2. BGP
  3. EIGRP Correct answer.
  4. RIP

Explanation

EIGRP uses the Diffusing Update Algorithm (DUAL) to compute loop-free paths and maintain a topology table with feasible successors, allowing fast convergence without routing loops. OSPF uses the Shortest Path First algorithm, RIP uses split horizon and hold-down timers, and BGP uses path-vector attributes, none of which use the feasible successor concept.

Question 41Communication Networks and Protocols

Which OSI layer is responsible for logical addressing and routing of packets between different networks?

  1. Session layer
  2. Network layer Correct answer.
  3. Data link layer
  4. Transport layer

Explanation

The network layer handles logical (IP) addressing and determines the path packets take across interconnected networks through routing. The data link layer deals only with local frame delivery, while transport and session layers operate above routing concerns.

Question 42Communication Networks and Protocols

A host with IP address 192.168.10.130 and subnet mask 255.255.255.192 belongs to which subnet address?

  1. 192.168.10.192
  2. 192.168.10.0
  3. 192.168.10.64
  4. 192.168.10.128 Correct answer.

Explanation

A /26 mask (255.255.255.192) creates subnets in blocks of 64 in the last octet: 0, 64, 128, 192. The address 130 falls in the 128-191 range, so the subnet address is 192.168.10.128.

Question 43Communication Networks and Protocols

Which transport protocol provides reliable, connection-oriented delivery with acknowledgements and retransmission?

  1. UDP
  2. ARP
  3. TCP Correct answer.
  4. ICMP

Explanation

TCP establishes a connection through a three-way handshake and guarantees ordered, reliable delivery using sequence numbers and acknowledgements. UDP is connectionless and best-effort, while ICMP and ARP are not transport protocols.

Question 44Communication Networks and Protocols

In the TCP three-way handshake, which flags are set in the second segment sent by the server?

  1. SYN only
  2. FIN and ACK
  3. ACK only
  4. SYN and ACK Correct answer.

Explanation

The client initiates with a SYN, and the server replies with a segment that both acknowledges the client's sequence number (ACK) and synchronizes its own sequence number (SYN). The client then completes the handshake with an ACK.

Question 45Communication Networks and Protocols

Which DNS record type maps a hostname to an IPv6 address?

  1. MX
  2. AAAA Correct answer.
  3. A
  4. CNAME

Explanation

An AAAA record stores a 128-bit IPv6 address for a hostname. The A record holds an IPv4 address, MX identifies mail servers, and CNAME creates an alias to another name.

Question 46Communication Networks and Protocols

What is the primary purpose of the Address Resolution Protocol (ARP)?

  1. Translate private addresses to public addresses
  2. Resolve an IP address to a MAC address on the local link Correct answer.
  3. Assign IP addresses dynamically to hosts
  4. Resolve a MAC address to an IP address

Explanation

ARP broadcasts a request asking which device owns a given IPv4 address, and the owner replies with its MAC address so frames can be delivered on the local link. The reverse mapping is handled by other mechanisms, and address assignment and translation are separate functions.

Question 47Communication Networks and Protocols

Which protocol uses a link-state database and runs the Dijkstra shortest-path algorithm to compute routes within a single autonomous system?

  1. RIP
  2. OSPF Correct answer.
  3. BGP
  4. SNMP

Explanation

OSPF is an interior gateway protocol that floods link-state advertisements so every router builds an identical topology database, then runs Dijkstra's algorithm to compute shortest paths. BGP is used between autonomous systems, RIP uses distance-vector hop counts, and SNMP is for management.

Question 48Communication Networks and Protocols

A company is allocated 10.0.0.0/22. How many usable host addresses does this block provide?

  1. 510
  2. 2046
  3. 1022 Correct answer.
  4. 1024

Explanation

A /22 leaves 10 host bits, giving 2^10 = 1024 total addresses. Subtracting the network and broadcast addresses yields 1022 usable host addresses.

Question 49Communication Networks and Protocols

Which device forwards frames based on MAC addresses and maintains a table mapping MAC addresses to switch ports?

  1. Router
  2. Layer 2 switch Correct answer.
  3. Repeater
  4. Hub

Explanation

A Layer 2 switch learns source MAC addresses and the ports they arrive on, building a forwarding table so frames are sent only to the correct port. Routers forward on IP addresses, while hubs and repeaters simply regenerate signals to all ports.

Question 50Communication Networks and Protocols

What is the default VLAN behavior described by IEEE 802.1Q tagging on a trunk link?

  1. Only the native VLAN is permitted across the trunk
  2. The native VLAN frames are sent untagged while other VLANs are tagged Correct answer.
  3. Tags are inserted only into the payload of TCP segments
  4. All frames are tagged with the native VLAN identifier

Explanation

802.1Q inserts a VLAN tag into the Ethernet frame for most VLANs, but frames belonging to the native VLAN are transmitted untagged so that legacy devices can interoperate. Both sides must agree on the native VLAN to avoid mismatches.