CompTIA Network+ Revision

What are the seven OSI layers from 1 to 7?

Physical, Data Link, Network, Transport, Session, Presentation, Application.

Which OSI layer sends raw bits over a medium?

Layer 1, Physical.

Which OSI layer handles Ethernet frames and MAC addressing?

Layer 2, Data Link.

Which OSI layer handles IP addressing and routing?

Layer 3, Network.

Which OSI layer handles TCP and UDP?

Layer 4, Transport.

Which OSI layer manages application conversations?

Layer 5, Session.

Which OSI layer handles translation, formatting, and encryption representation?

Layer 6, Presentation.

Which OSI layer provides network services to applications?

Layer 7, Application.

What is the Layer 2 protocol data unit?

Frame.

What is the Layer 3 protocol data unit?

Packet.

What is the Layer 4 TCP protocol data unit?

Segment.

What is the Layer 4 UDP protocol data unit?

Datagram.

What is encapsulation?

Adding protocol headers and sometimes trailers as data moves down a network stack.

What is decapsulation?

Removing protocol headers and trailers as received data moves up a stack.

Which OSI layer does a traditional Ethernet switch primarily operate at?

Layer 2.

Which OSI layer does a router primarily operate at?

Layer 3.

Which OSI layer does a hub operate at?

Layer 1.

What is the TCP three-way handshake?

SYN, SYN-ACK, ACK.

What makes TCP reliable?

Sequence numbers, acknowledgments, retransmissions, and flow control.

How does UDP differ from TCP?

UDP is connectionless and does not inherently guarantee delivery or ordering.

What is ICMP used for?

IP error reporting and diagnostics, including ping and traceroute messages.

What is the IPv4 Don't Fragment flag?

A flag that prevents routers from fragmenting a packet; an oversized packet triggers an ICMP error.

What is an Ethernet MAC address?

A typically 48-bit Layer 2 identifier for a network interface.

What is unicast?

One sender communicating with one destination.

What is broadcast?

One sender transmitting to all devices in a broadcast domain.

What is multicast?

One sender delivering traffic to a subscribed group.

What is anycast?

Multiple devices share an address; routing delivers traffic to a selected nearby instance.

What is full-duplex communication?

Both endpoints can transmit and receive simultaneously.

What is half-duplex communication?

Devices take turns transmitting and receiving.

What is MTU?

Maximum Transmission Unit; the largest network-layer packet carried in a link-layer payload without fragmentation.

What is latency?

Time required for data to travel from source to destination.

What is jitter?

Variation in packet delay.

What is packet loss?

Packets that fail to reach their destination.

What is throughput?

Actual successfully delivered data rate.

What is bandwidth?

Capacity of a communication channel.

What is a collision domain?

A network segment where simultaneous transmissions can interfere, typical of shared half-duplex Ethernet.

What is a broadcast domain?

A group of devices that receive the same Layer 2 broadcast traffic.

What is the difference between a switch and a router?

A switch primarily forwards frames using MAC addresses; a router forwards packets between IP networks.

What is the TCP/IP model's typical four-layer order?

Link, Internet, Transport, Application.

What is ARP?

IPv4 Address Resolution Protocol; maps a local IPv4 address to a MAC address.

What is NDP?

IPv6 Neighbor Discovery Protocol; uses ICMPv6 for neighbor and router discovery.

What is a star topology?

Endpoints connect to a central switch or hub.

What is a bus topology?

Devices share a common backbone medium.

What is a ring topology?

Devices connect in a closed loop.

What is a full mesh topology?

Every node connects directly to every other node.

What is a partial mesh topology?

Some nodes have multiple redundant links, but not all pairs connect.

What is a hybrid topology?

A network combining two or more topology patterns.

What is a point-to-point link?

A dedicated connection between two endpoints.

What is a point-to-multipoint topology?

One central device communicates with multiple endpoints.

What is a LAN?

Local Area Network, usually within a site or building.

What is a WAN?

Wide Area Network connecting geographically separated sites.

What is a WLAN?

Wireless Local Area Network.

What is a PAN?

Personal Area Network connecting nearby personal devices.

What is a MAN?

Metropolitan Area Network spanning a city or metro region.

What is a SAN?

Storage Area Network providing block-level storage access.

What is a CAN?

Campus Area Network linking multiple buildings on a campus.

What is the demarcation point?

The boundary where the service provider's responsibility meets customer premises wiring.

What is a smart jack or NIU?

Provider termination equipment offering diagnostics and an interface to a WAN circuit.

What is CPE?

Customer Premises Equipment at the subscriber site.

What is a CSU/DSU?

Equipment historically used to connect a router to a digital leased-line circuit.

What is an ONT?

Optical Network Terminal converting a provider's optical access service to customer interfaces.

What is a modem?

Device modulating and demodulating signals for a provider access technology.

What is a DSLAM?

Digital Subscriber Line Access Multiplexer aggregating subscriber DSL lines.

What is a CMTS?

Cable Modem Termination System aggregating cable broadband connections.

What is DOCSIS?

Data Over Cable Service Interface Specification for broadband over cable networks.

What is a leased line?

A dedicated provider circuit between locations.

What is MPLS?

Multiprotocol Label Switching; forwards traffic using labels in provider networks.

What is Metro Ethernet?

Carrier-provided Ethernet connectivity across a metropolitan area.

What is SD-WAN?

Software-defined WAN that centrally manages policy and paths across WAN connections.

What is a site-to-site VPN?

Encrypted tunnel connecting networks at separate sites.

What is a client-to-site VPN?

Remote-user VPN connecting an endpoint into an organization network.

What is broadband?

High-capacity access service commonly shared or statistically multiplexed.

What is satellite WAN connectivity?

Connectivity via satellite, useful in remote areas but subject to link latency and coverage constraints.

What is a cellular WAN?

WAN connectivity using mobile networks such as 4G or 5G.

What is a hot site?

A disaster-recovery site with infrastructure ready for rapid operation.

What is a warm site?

A partially prepared recovery site requiring some setup.

What is a cold site?

A recovery facility with basic space/utilities but little ready-to-run equipment.

What is high availability?

Designing services to remain operational despite component failures.

What is failover?

Automatically or manually moving service to a backup component or path.

What is load balancing?

Distributing traffic or workloads across multiple resources.

What is redundancy?

Duplicate components or paths that reduce single points of failure.

What is a hypervisor?

Software or firmware that hosts and manages virtual machines.

What is a Type 1 hypervisor?

Bare-metal hypervisor running directly on hardware.

What is a Type 2 hypervisor?

Hosted hypervisor running on an existing operating system.

What is a virtual switch?

Software switching function connecting VMs and virtual interfaces.

What is a virtual NIC?

Software-defined network interface presented to a virtual machine.

What is a virtual router?

Routing functionality implemented in software or a virtual appliance.

What is a virtual firewall?

Firewall functionality deployed as software or a virtual appliance.

What is VLAN tagging?

Adding an IEEE 802.1Q tag to identify a frame's VLAN.

What is an access port?

A switch port carrying traffic for one VLAN, usually untagged.

What is a trunk port?

A switch link carrying multiple VLANs using tagging.

What is the native VLAN?

VLAN typically carried untagged on an 802.1Q trunk when configured.

What is a VLAN?

A logical Layer 2 broadcast-domain separation.

What is VXLAN?

Overlay encapsulation that extends Layer 2 segments over a Layer 3 underlay.

What is a VNI?

VXLAN Network Identifier identifying an overlay segment.

What is network segmentation?

Dividing a network into isolated or controlled security/traffic zones.

What is microsegmentation?

Fine-grained security policy between workloads, often enforced virtually.

What is port mirroring?

Copying traffic from a port or VLAN to a monitoring destination.

What is live VM migration?

Moving a running VM between hosts with minimal interruption.

What is a network overlay?

Logical network built over an underlying physical network.