98 questions
Which layer of the OSI model is responsible for logical addressing and determining the best path for packets across an internetwork?
- a.Layer 1 (Physical)
- b.Layer 4 (Transport)
- c.Layer 3 (Network)✓
- d.Layer 2 (Data Link)
Layer 3, the Network layer, handles logical addressing such as IP and makes routing decisions to move packets between networks. The Data Link layer uses physical MAC addresses for local delivery, while the Transport layer manages end-to-end segmentation. Routers operate primarily at Layer 3.
A network administrator needs to identify the protocol data unit (PDU) used at the Transport layer of the OSI model. Which term applies?
- a.Packet
- b.Bit
- c.Frame
- d.Segment✓
At the Transport layer the PDU is called a segment (or datagram for UDP). Packets exist at the Network layer, frames at the Data Link layer, and bits at the Physical layer. Knowing PDU names per layer helps when interpreting protocol behavior.
Which protocol and port number are used by HTTPS for secure web traffic by default?
- a.TCP 443✓
- b.UDP 53
- c.TCP 80
- d.TCP 22
HTTPS uses TCP port 443 and secures web traffic with TLS. Port 80 is plain HTTP, port 53 is DNS, and port 22 is SSH. Memorizing well-known ports is essential for firewall and troubleshooting work.
What is the default port used by the Domain Name System (DNS) for standard name resolution queries?
- a.TCP 110
- b.UDP 53✓
- c.TCP 25
- d.UDP 67
DNS uses UDP port 53 for most standard queries because they are small and benefit from low overhead. TCP 53 is used for zone transfers and larger responses. Ports 25, 110, and 67 belong to SMTP, POP3, and DHCP respectively.
An engineer must choose an address class for a private network that supports up to 500 hosts on a single subnet. Which private range is most appropriate to draw from?
- a.10.0.0.0/8✓
- b.224.0.0.0/4
- c.127.0.0.0/8
- d.169.254.0.0/16
The 10.0.0.0/8 range is an RFC 1918 private block that easily provides subnets large enough for 500 hosts. 169.254.0.0/16 is APIPA link-local, 224.0.0.0/4 is multicast, and 127.0.0.0/8 is loopback. Private ranges avoid public IP consumption.
How many usable host addresses are available in a subnet with a /29 prefix?
- a.4
- b.8
- c.2
- d.6✓
A /29 leaves 3 host bits, giving 2^3 = 8 total addresses, minus the network and broadcast addresses, for 6 usable hosts. Subnetting math requires subtracting two reserved addresses from the total. /29 subnets are common for small point-to-point or device segments.
Which IPv6 address type begins with the prefix FE80::/10 and is used only for communication on the local link?
- a.Link-local✓
- b.Global unicast
- c.Anycast
- d.Multicast
Link-local IPv6 addresses use the FE80::/10 prefix and are auto-configured on every interface for local-link communication. Global unicast addresses are routable on the internet, while multicast uses FF00::/8. Link-local addresses are never routed beyond the local segment.
A star topology relies on which central device to interconnect all end nodes?
- a.A central switch or hub✓
- b.A ring of daisy-chained cables
- c.A repeater between each pair of nodes
- d.A shared coaxial bus
In a star topology every node connects to a central switch or hub, which forwards traffic between them. A failure of one cable affects only that node, improving fault isolation. Bus and ring topologies use shared media that create single points of failure.
Which cabling standard defines the maximum supported distance of 100 meters for a twisted-pair Ethernet run?
- a.1000BASE-LX
- b.10GBASE-ER
- c.1000BASE-T✓
- d.100BASE-FX
1000BASE-T runs over twisted-pair copper and is limited to 100 meters per segment. The other options are fiber standards that support much longer distances. The 100-meter copper limit includes patch cords and horizontal cabling.
What is the primary purpose of a VLAN in a switched network?
- a.To convert Layer 2 frames into Layer 3 packets
- b.To provide power to connected devices
- c.To increase the speed of individual switch ports
- d.To logically segment a physical switch into separate broadcast domains✓
A VLAN logically segments a switch so that ports belong to separate broadcast domains without needing additional physical switches. This improves security and reduces broadcast traffic. Routing between VLANs still requires a Layer 3 device.
Which protocol resolves an IPv4 address to a MAC address on a local Ethernet segment?
- a.ARP✓
- b.ICMP
- c.DNS
- d.NTP
ARP (Address Resolution Protocol) maps a known IPv4 address to the MAC address needed for Layer 2 delivery. DNS resolves names to IPs, ICMP handles diagnostics, and NTP synchronizes time. ARP operates only within a local broadcast domain.
A company wants clients to obtain IP configuration automatically. Which protocol assigns addresses, subnet masks, gateways, and DNS servers dynamically?
- a.LDAP
- b.DHCP✓
- c.SNMP
- d.DNS
DHCP dynamically leases IP addresses along with subnet mask, default gateway, and DNS server information to clients. This eliminates manual configuration and reduces addressing errors. DHCP uses UDP ports 67 and 68 for server and client communication.
In the TCP three-way handshake, which sequence of flags correctly establishes a connection?
- a.ACK, SYN-ACK, SYN
- b.SYN, SYN-ACK, ACK✓
- c.PSH, URG, ACK
- d.FIN, ACK, RST
The TCP three-way handshake proceeds as SYN, then SYN-ACK, then ACK to establish a reliable session. FIN and RST relate to closing or resetting connections. Understanding the handshake helps diagnose connection setup failures.
Which cloud service model provides virtual machines, storage, and networking that customers manage themselves?
- a.PaaS
- b.IaaS✓
- c.DaaS
- d.SaaS
Infrastructure as a Service (IaaS) delivers fundamental compute, storage, and network resources that the customer configures and manages. SaaS delivers finished applications, and PaaS provides a development platform. IaaS offers the most customer control among cloud models.
What distinguishes UDP from TCP at the Transport layer?
- a.UDP guarantees ordered delivery through sequencing
- b.UDP always encrypts application data
- c.UDP performs a three-way handshake before sending data
- d.UDP is connectionless and does not guarantee delivery✓
UDP is connectionless, has low overhead, and does not guarantee delivery, ordering, or retransmission. This makes it ideal for latency-sensitive traffic such as VoIP and streaming. TCP, by contrast, is connection-oriented and reliable.
A /24 network needs to be divided into four equal subnets. Which new prefix length should be used?
- a./27
- b./28
- c./26✓
- d./25
Borrowing two host bits from a /24 creates four subnets, resulting in a /26 prefix. Each /26 subnet provides 62 usable hosts. The formula 2^n subnets requires n borrowed bits, so 2^2 equals four subnets.
Which network device forwards frames based on MAC address tables and operates primarily at Layer 2?
- a.Firewall
- b.Router
- c.Switch✓
- d.Load balancer
A switch builds a MAC address table and forwards frames only to the port associated with the destination MAC, operating at Layer 2. Routers work at Layer 3 using IP addresses. Switching reduces collisions by creating dedicated collision domains per port.
Which IEEE standard defines VLAN tagging on Ethernet trunk links?
- a.802.1Q✓
- b.802.11ac
- c.802.1X
- d.802.3af
IEEE 802.1Q defines the frame tagging method used to carry multiple VLANs across a trunk link. 802.3af covers PoE, 802.11ac is Wi-Fi, and 802.1X is port-based access control. The 802.1Q tag adds a 4-byte field to the Ethernet frame.
What is the purpose of a default gateway on a host's IP configuration?
- a.To resolve domain names into IP addresses
- b.To encrypt outbound traffic automatically
- c.To assign IP addresses to other hosts
- d.To forward traffic destined for remote networks✓
The default gateway is the router interface a host uses to reach destinations outside its local subnet. Without it, a host can only communicate on its own network. Traffic for remote networks is sent to the gateway for further routing.
Which frequency band and standard pairing offers wider channels and higher throughput but shorter range?
- a.2.4 GHz with 802.11g
- b.2.4 GHz with 802.11b
- c.900 MHz with 802.11ah
- d.5 GHz with 802.11ac✓
802.11ac operates in the 5 GHz band, offering wider channels and higher throughput at the cost of shorter range and less obstacle penetration. The 2.4 GHz band travels farther but is more congested and slower. Band selection balances speed against coverage.
Which protocol uses TCP port 22 to provide encrypted remote command-line access?
- a.SSH✓
- b.FTP
- c.RDP
- d.Telnet
SSH uses TCP port 22 to provide an encrypted remote shell, replacing insecure protocols like Telnet. Telnet on port 23 sends data in clear text. SSH is the standard for secure device management.
In a client-server architecture, what best describes the role of the server?
- a.It exclusively resolves MAC addresses to IPs
- b.It provides resources or services in response to client requests✓
- c.It only forwards broadcast traffic between subnets
- d.It generates spanning-tree topology changes
A server centrally provides resources or services such as files, web pages, or databases in response to client requests. Clients initiate requests and consume those services. This model contrasts with peer-to-peer where nodes act as both.
Which address is reserved as the IPv4 loopback used to test the local TCP/IP stack?
- a.10.0.0.1
- b.127.0.0.1✓
- c.255.255.255.255
- d.192.168.0.1
127.0.0.1 is the loopback address that lets a host test its own TCP/IP stack without touching the physical network. The entire 127.0.0.0/8 block is reserved for loopback. Pinging it confirms the local protocol stack is functioning.
Which OSI layer provides reliable, connection-oriented delivery with segmentation, sequencing, and flow control?
- a.Layer 4 (Transport)✓
- b.Layer 5 (Session)
- c.Layer 3 (Network)
- d.Layer 6 (Presentation)
The Transport layer (Layer 4) handles end-to-end delivery, breaking data into segments, sequencing them, and managing flow control and, in TCP, retransmission. The Network layer routes packets but does not guarantee delivery. TCP is the classic Layer 4 protocol that provides these reliability features.
At which OSI layer are data formatting, character encoding, compression, and encryption or decryption handled?
- a.Layer 7 (Application)
- b.Layer 2 (Data Link control)
- c.Layer 4 (Transport)
- d.Layer 6 (Presentation)✓
The Presentation layer (Layer 6) translates data between the application and the network, handling formatting, character encoding, compression, and encryption. It ensures data from the sender is readable by the receiver. TLS encryption is often associated with this layer's functions.
Which OSI layer establishes, maintains, and terminates dialogues between two communicating hosts?
- a.Layer 4 (Transport)
- b.Layer 5 (Session)✓
- c.Layer 7 (Application)
- d.Layer 6 (Presentation)
The Session layer (Layer 5) sets up, manages, and tears down the sessions or dialogues between applications on different hosts. It can also handle checkpointing and reestablishing dropped connections. It sits above Transport and below Presentation in the stack.
Which OSI layer defines voltage levels, pin assignments, and the encoding of bits into electrical, optical, or radio signals?
- a.Layer 4 (Transport)
- b.Layer 3 (Network)
- c.Layer 2 (Data Link)
- d.Layer 1 (Physical)✓
The Physical layer (Layer 1) defines the physical and electrical characteristics of the medium, including voltage, pinouts, cabling, and how bits become signals. Hubs, cables, and connectors operate here. It is concerned only with transmitting raw bits, not their meaning.
The Data Link layer encapsulates packets into which protocol data unit before placing them on the local medium?
- a.Packet
- b.Frame✓
- c.Datagram
- d.Segment
At the Data Link layer (Layer 2), packets from the Network layer are encapsulated into frames that include source and destination MAC addresses and error-checking. Segments belong to the Transport layer and packets to the Network layer. Framing prepares data for delivery across the local link.
Protocols such as HTTP, SMTP, and FTP that provide services directly to user applications operate at which OSI layer?
- a.Layer 5 (Session)
- b.Layer 6 (Presentation)
- c.Layer 7 (Application)✓
- d.Layer 4 (Transport)
The Application layer (Layer 7) is where protocols that interface directly with user-facing applications, such as HTTP, SMTP, and FTP, operate. It provides network services to applications rather than to end users directly. It is the top layer of the OSI model.
As data moves down the OSI stack from a sending host, in what order is it encapsulated?
- a.Bits, frames, packets, segments, data
- b.Packets, segments, frames, data, bits
- c.Data, segments, packets, frames, bits✓
- d.Frames, packets, segments, data, bits
Encapsulation proceeds top down: application data becomes segments at Transport, packets at Network, frames at Data Link, and finally bits at the Physical layer. Each layer adds its own header (and the Data Link layer a trailer). The receiving host reverses this order during de-encapsulation.
At the Network layer, a segment received from the Transport layer is encapsulated into which protocol data unit?
- a.Segment
- b.Packet✓
- c.Bit
- d.Frame
The Network layer (Layer 3) adds logical addressing to form a packet from the Transport layer's segment. Frames are formed at Layer 2 and bits exist at Layer 1. Routers forward packets based on the destination IP in the Layer 3 header.
In a full-mesh topology of 6 nodes, how many direct point-to-point links are required?
- a.15✓
- b.30
- c.6
- d.12
A full mesh connects every node to every other node, requiring n(n-1)/2 links. For 6 nodes that is 6 times 5 divided by 2, which equals 15. Full mesh offers maximum redundancy but grows expensive quickly as nodes increase.
Which topology connects multiple remote sites back to a single central hub site, minimizing links but creating a single point of failure at the center?
- a.Bus
- b.Ring
- c.Full mesh
- d.Hub-and-spoke✓
In a hub-and-spoke topology, each remote spoke site connects only to a central hub, reducing the number of links compared with a mesh. The trade-off is that the hub becomes a single point of failure and a potential bottleneck. It is common in WAN designs for cost efficiency.
Which data center fabric design connects every leaf switch to every spine switch to provide predictable, low-latency east-west traffic?
- a.Token ring
- b.Three-tier collapsed core
- c.Bus backbone
- d.Spine-and-leaf✓
A spine-and-leaf fabric links each leaf (access) switch to every spine switch, so any server is at most two hops from any other. This yields consistent latency and high bandwidth for east-west traffic in modern data centers. It scales better than traditional three-tier designs for server-to-server flows.
In the classic three-tier hierarchical campus model, which layer aggregates access switches and enforces routing and policy between them?
- a.Distribution layer✓
- b.Physical layer
- c.Core layer
- d.Access layer
The distribution (aggregation) layer sits between access and core, aggregating access-layer uplinks and applying routing, filtering, and policy. The access layer connects end devices, and the core provides high-speed backbone transport. Separating these roles improves scalability and manageability.
Which network type spans a city or metropolitan area, larger than a LAN but smaller than a WAN?
- a.SAN
- b.PAN
- c.MAN✓
- d.WLAN
A Metropolitan Area Network (MAN) covers a city or metro region, bridging the gap between a local LAN and a wide-area WAN. It often interconnects multiple campuses within the same city. Service providers frequently deliver MAN services over fiber.
Which specialized network provides block-level access to consolidated storage, appearing to servers as locally attached disks?
- a.Campus area network (CAN)
- b.Personal area network (PAN)
- c.Wireless LAN (WLAN)
- d.Storage area network (SAN)✓
A Storage Area Network (SAN) delivers block-level storage over a dedicated high-speed network so servers treat remote volumes as if locally attached. Technologies include Fiber Channel and iSCSI. This differs from file-level NAS, which presents shares over the LAN.
A wireless connection between a smartphone and nearby earbuds over Bluetooth is an example of which network type?
- a.Storage area network (SAN)
- b.Personal area network (PAN)✓
- c.Metro area network (MAN)
- d.Wide area network (WAN)
A Personal Area Network (PAN) interconnects devices within a person's immediate range, typically a few meters, often over Bluetooth. Pairing a phone with earbuds or a smartwatch is a common example. PANs are the smallest scope among network types.
Which technology uses centralized, software-based policy to steer traffic across multiple transport links such as MPLS, broadband, and LTE between sites?
- a.VLSM
- b.STP
- c.PoE
- d.SD-WAN✓
Software-Defined WAN (SD-WAN) abstracts the underlying transports and uses centralized policy to route application traffic over the best available link. It can combine MPLS, broadband, and cellular for resilience and cost savings. It improves agility compared with traditional static WAN routing.
Which copper cabling category is required to reliably support 10GBASE-T over the full 100-meter distance?
- a.Cat 3
- b.Cat 6a✓
- c.Cat 5e
- d.Cat 5
Category 6a cabling supports 10GBASE-T at the full 100-meter distance with improved alien crosstalk performance. Cat 6 can carry 10 Gbps but only to about 55 meters. Cat 5e tops out at 1 Gbps for typical runs.
Which small-form-factor fiber connector uses a 1.25 mm ferrule and a latching clip, and is common on SFP transceivers?
- a.LC✓
- b.BNC
- c.F-type
- d.ST
The LC (Lucent Connector) uses a compact 1.25 mm ferrule and a push-pull latch, making it ideal for high-density SFP and SFP+ ports. ST and SC are larger 2.5 mm connectors. BNC and F-type are coaxial, not fiber, connectors.
Which transceiver form factor supports a single 10 Gbps link and is widely used in switch uplinks?
- a.RJ45
- b.SFP+✓
- c.GBIC
- d.QSFP28 (100 Gbps quad channel)
SFP+ is an enhanced small form-factor pluggable transceiver rated for 10 Gbps on a single lane. GBIC is an older, larger 1 Gbps module. QSFP variants bundle four lanes for 40 or 100 Gbps, so they are not single-link 10 Gbps modules.
Which fiber type uses a larger core, typically 50 or 62.5 microns, with LED or VCSEL light sources for shorter, cost-effective runs?
- a.Multimode fiber✓
- b.Single-mode fiber
- c.Twinaxial cable
- d.Coaxial cable
Multimode fiber has a larger core that allows multiple light paths, working well for shorter distances with inexpensive LED or VCSEL sources. Single-mode fiber has a tiny core and laser sources for very long distances. Multimode is common inside data centers and buildings.
Which cable rating is required when cabling runs through air-handling spaces because it produces less toxic smoke when burned?
- a.Riser (CMR)
- b.Shielded (STP)
- c.Direct-burial
- d.Plenum (CMP)✓
Plenum-rated cable (CMP) has a fire-resistant jacket that emits less toxic smoke, so it is required in plenum air spaces above ceilings or under raised floors. Riser cable is for vertical shafts between floors but not plenum spaces. Local fire codes mandate plenum cable in these areas.
Which connector is threaded onto coaxial cable to deliver cable-internet or CATV service to a modem?
- a.LC
- b.RJ11
- c.SC
- d.F-type✓
The F-type connector screws onto coaxial cable and is standard for cable television and cable-modem internet service. LC and SC are fiber connectors, while RJ11 is for telephone lines. Coax with F-connectors is common on the last mile of cable networks.
Which short-reach copper assembly with attached transceivers, known as a DAC, is commonly used for top-of-rack switch-to-server links?
- a.Coaxial RG-6
- b.Twinaxial cable✓
- c.Single-mode fiber
- d.Cat 5e patch cord
A Direct Attach Copper (DAC) cable uses twinaxial copper with transceivers permanently attached to each end, providing a low-cost, low-power option for short 10 to 100 Gbps links inside a rack. It is cheaper than optics for these short distances. It is popular for top-of-rack connectivity.
Which fiber connector bundles 12 or more fibers into one housing and is often used to break out 40G or 100G into multiple lanes?
- a.ST
- b.MPO/MTP✓
- c.SC simplex
- d.LC duplex
The MPO/MTP connector groups many fibers (commonly 12 or 24) into a single rectangular housing, enabling high-density parallel optics for 40G and 100G. It can be broken out into multiple duplex LC links. It is widely used in data-center fiber trunking.
A traditional analog telephone line typically terminates in which small connector with fewer conductors than an Ethernet jack?
- a.LC
- b.RJ45
- c.BNC
- d.RJ11✓
The RJ11 connector, with its two to four conductors, is used for analog telephone and some DSL connections. RJ45 is the eight-conductor connector used for Ethernet. The two look similar but RJ11 is noticeably narrower.
How many usable host addresses does a /26 subnet provide?
- a.126
- b.30
- c.64
- d.62✓
A /26 leaves 6 host bits, giving 2 to the 6th power, or 64 total addresses, minus the network and broadcast addresses, for 62 usable hosts. Always subtract two reserved addresses from the total. A /26 is a common size for medium departmental subnets.
The subnet mask 255.255.255.240 corresponds to which CIDR prefix length?
- a./27
- b./29
- c./28✓
- d./26
The last octet 240 is 11110000 in binary, which is four network bits added to the 24 in the first three octets, totaling 28. So 255.255.255.240 equals /28. Each /28 subnet provides 14 usable hosts.