SAIL MCQs

Explanation: Traditionally one address identifies the network and one is the broadcast address, leaving 256-2=254 usable host addresses.

Explanation: With a /24 prefix, the final 8 bits are host bits; setting all of them to 1 gives 192.168.10.255.

Explanation: MAC addresses are used for Layer-2 frame delivery on technologies such as Ethernet.

Explanation: Standard Ethernet MAC addresses are 48 bits, commonly written as six hexadecimal octets.

Explanation: ARP resolves an IPv4 address to the corresponding link-layer MAC address on the local network.

Explanation: The Domain Name System maps human-readable names to IP addresses and stores other DNS resource records.

Explanation: DHCP can dynamically supply IP address, subnet mask, default gateway, DNS-server information and other network parameters.

Explanation: TCP establishes a connection and provides sequencing, acknowledgements and retransmission for reliable ordered delivery.

Explanation: The traditional TCP/IP model has four layers: Application, Transport, Internet, and Network Access.

Explanation: The TCP/IP Internet layer provides logical addressing and packet routing functions similar to the OSI Network layer.

Explanation: IPv4 addresses are 32 bits long, normally written as four decimal octets.

Explanation: SMTP is the standard application-layer protocol used to submit and relay email messages.

Explanation: FTP stands for File Transfer Protocol and is designed for transferring files between networked systems.

Explanation: A star topology connects each endpoint to a central hub or, more commonly today, an Ethernet switch.

Explanation: A classic bus network uses a shared backbone cable to which nodes are attached.

Explanation: IEEE 802.3 specifies Ethernet technologies.

Explanation: A switch builds a MAC address table from source addresses and uses it to forward known unicast frames only toward the appropriate destination port.

Explanation: UDP sends independent datagrams without connection establishment or built-in retransmission and ordering mechanisms.

Explanation: TCP's acknowledgement, sequencing and retransmission mechanisms make it appropriate when reliable delivery is required.

Explanation: TCP and UDP ports allow incoming traffic to be delivered to the appropriate application/process endpoint.

Explanation: HTTP conventionally uses TCP port 80 by default.

Explanation: HTTPS conventionally uses TCP port 443.

Explanation: 10.0.0.0/8 is one of the IPv4 address blocks reserved for private networks.

Explanation: The private 172.16.0.0/12 range extends from 172.16.0.0 through 172.31.255.255.

Explanation: IPv4 addresses in 127.0.0.0/8 are reserved for loopback; 127.0.0.1 is commonly used as localhost.

Explanation: IPv6 uses 128-bit addresses, providing a much larger address space than IPv4.

Explanation: IPv6 addresses are normally represented as hexadecimal groups separated by colons, with permitted compression rules.

Explanation: The network address is .64 and broadcast is .127, leaving .65 through .126 for conventional host assignment.

Explanation: The default gateway is the router used to reach destinations not directly on the local subnet.

Explanation: Network Address Translation commonly allows privately addressed hosts to communicate through public IPv4 addressing at the network boundary.

Explanation: Port Address Translation tracks flows using address and transport-port information so many internal connections can share one public address.

Explanation: ICMP carries control, error and diagnostic information for IP networks.

Explanation: Ping normally sends ICMP Echo Request messages and listens for Echo Reply messages.

Explanation: Traceroute exploits IP hop-limit/TTL behavior and returned control messages to reveal routers along a path.

Explanation: Each router forwarding an IPv4 packet decrements TTL, helping prevent packets from circulating indefinitely.

Explanation: Routers compare destination IP addresses with routing-table prefixes to determine how packets should be forwarded.

Explanation: Longest-prefix matching selects the most specific matching network route.

Explanation: VLANs logically segment a switched Ethernet network into distinct Layer-2 broadcast domains.

Explanation: IPv6 reserves ::1 as the loopback address.

Explanation: A /26 prefix leaves 6 host bits, so the subnet contains 2^6=64 total addresses.

Explanation: A /26 contains 64 total addresses; excluding network and broadcast addresses leaves 62 conventional usable host addresses.

Explanation: A /26 mask has 26 leading 1 bits, giving 255.255.255.192.

Explanation: A /26 block has 64 addresses. The block beginning at .64 ends at .127, which is its broadcast address.

Explanation: Modern switched Ethernet gives each port its own collision domain, unlike a shared hub segment.

Explanation: Communication between separate VLAN IP networks requires a Layer-3 device or Layer-3 switching function.

Explanation: The IEEE 802.11 family specifies wireless LAN technologies commonly known as Wi-Fi.

Explanation: A firewall permits, blocks or otherwise controls network traffic according to configured security policy and inspection capabilities.

Explanation: A /27 contains 32 total addresses; excluding network and broadcast addresses leaves 30 conventional usable host addresses.

Explanation: A /27 mask has 27 leading 1 bits, giving 255.255.255.224.

Explanation: A /27 prefix leaves 5 host bits, so it contains 2^5=32 total IPv4 addresses.

Explanation: Successful IP connectivity with failed name-based access commonly indicates a DNS resolution problem.

Explanation: DHCP supplies dynamic IP configuration such as address, mask, gateway and DNS-server information.

Explanation: A /27 has blocks of 32 addresses. The block starting at .96 ends at .127, its broadcast address.

Explanation: A /26 provides 64 total and 62 conventional usable addresses; /27 provides only 30 usable addresses.

Explanation: 100 megabits per second for 2 seconds gives 200 megabits, or about 200 million bits.

Explanation: Time=data/rate=80 Mbit/20 Mbit/s=4 seconds.

Explanation: 10 MB×8 bits/byte=80 megabits under the stated decimal-unit assumption.

Explanation: TCP normally establishes a connection using the three-way handshake SYN → SYN-ACK → ACK.

Explanation: TCP sequence numbers identify byte positions, enabling ordered reassembly and detection/recovery of missing data.

Explanation: TCP acknowledgements communicate reception progress and support reliable delivery.

Explanation: TCP can retransmit data when acknowledgements or other loss-detection mechanisms indicate that data was not successfully delivered.

Explanation: The Frame Check Sequence contains a CRC value used to detect transmission errors in Ethernet frames.

Explanation: Unknown unicast traffic is normally flooded within the relevant VLAN until the destination location is learned.

Explanation: All 48 destination bits are 1 for the Ethernet broadcast address, written FF:FF:FF:FF:FF:FF.

Explanation: Routers separate Layer-2 broadcast domains and do not normally forward Ethernet broadcasts between IP networks.

Explanation: Local subnet traffic does not require a router, while remote-network traffic normally depends on a correctly configured and reachable default gateway.

Explanation: DHCP discovery begins with local broadcasts, so a relay can forward DHCP messages between client and server across router boundaries.

Explanation: Confidentiality protects information from unauthorized disclosure.

Explanation: Integrity concerns the correctness and trustworthiness of data and protection against unauthorized modification.

Explanation: Availability is the security objective of maintaining timely and reliable access to systems and information.

Explanation: Phishing uses deceptive messages or sites to manipulate users into disclosing information or taking unsafe actions.

Explanation: MFA adds an independent authentication factor, so possession of a password alone is less likely to be sufficient for account access.

Explanation: A Schmitt-trigger input uses different rising and falling switching thresholds, creating hysteresis that improves immunity to slowly varying or noisy inputs.

Explanation: When disabled, a tri-state output enters a high-impedance (Hi-Z) state so that it effectively disconnects from a shared bus.

Explanation: Disabled tri-state outputs present high impedance, allowing several devices to share conductors while preventing normal operation from having multiple active drivers at once.

Explanation: Opposing active drivers on the same line create bus contention, potentially causing excessive current and an undefined bus voltage.

Explanation: NMH = 4.4 − 3.2 = 1.2 V. It represents the allowable HIGH-level noise before the receiving input may no longer be guaranteed HIGH.

Explanation: Fan-out based on LOW-state current is IOL(max)/IIL = 16/1.6 = 10 loads.

Explanation: Minterms 1, 3, 5, and 7 are exactly the input combinations for which C=1, independent of A and B. Therefore F=C.

Explanation: A static-1 hazard is an unwanted 1→0→1 glitch caused by unequal propagation delays along different logic paths.

Explanation: By the consensus theorem, the consensus of AB and A̅C is BC. Adding BC provides overlapping coverage and can eliminate the static-1 hazard.

Explanation: In a ripple-carry adder, a carry may propagate serially through all four stages. The approximate worst-case carry delay is 4 × 12 ns = 48 ns.

Explanation: Carry look-ahead forms carry signals from generate and propagate terms in parallel, reducing the delay associated with a ripple-carry chain.

Explanation: A carry is generated by the bit position regardless of carry-in when both Ai and Bi are 1, hence Gi = AiBi.

Explanation: Signed overflow occurs when operands with the same sign produce a result with the opposite sign. For two positive operands, a negative-sign result indicates overflow.

Explanation: For two's-complement addition, overflow equals the XOR of the carry into the most significant sign bit and the carry out of that bit.

Explanation: A conventional PAL has a programmable AND plane feeding a fixed OR plane, while a PLA normally allows both planes to be programmed.

Explanation: The insulated MOS gate draws essentially no DC input current ideally; practical devices have small leakage and transient charging current.

Explanation: A common approximation is Pdynamic ≈ αCLVDD²f, where α is switching activity. Thus power rises strongly with supply voltage and switching frequency.

Explanation: The receiving flip-flop needs stable data before the clock edge, so Tclk ≥ 18 ns + 2 ns = 20 ns under the stated assumptions.

Explanation: Clock skew is the difference in arrival time of the same clock edge at different sequential elements.

Explanation: In a Moore FSM, outputs are functions of state only. In a Mealy FSM, outputs are functions of both present state and current inputs.

Explanation: Because Mealy outputs can depend directly on current inputs, some output distinctions that require separate Moore states can be represented without adding states.

Explanation: A single parity check changes whenever an odd number of bits are inverted, so all odd-number error patterns are detected; even-number patterns can escape detection.

Explanation: Hamming SEC requires 2^r ≥ m+r+1. With m=11, r=4 gives 16 ≥ 11+4+1 = 16, so four parity bits are sufficient.

Explanation: A code with dmin=3 can correct floor((dmin−1)/2)=1 error. It can detect up to two errors, but ordinary Hamming decoding cannot reliably correct two.

Explanation: A PLA generally has programmable AND and programmable OR arrays, providing more flexible sum-of-products implementation than a PAL with a fixed OR structure.

Explanation: Setup time requires data to be stable for 3 ns before the active edge, and hold time requires it to remain stable for 1 ns after the edge.

Explanation: A timing violation can leave a bistable element temporarily between valid logic states. This metastable condition eventually resolves, but its resolution time is not precisely predictable.

Explanation: The first flip-flop may become metastable, while the second provides additional resolution time before the signal is used by downstream synchronous logic, greatly reducing failure probability.