Network+ acronyms and glossary (N10-009)

Glossary

AAddress

The DNS record that maps a hostname to an IPv4 address. Its IPv6 counterpart is the AAAA record; a name can hold both so dual-stack clients can use either.N10-009 1.0 (Networking Concepts); 3.0 (Network Operations); 5.0 (Network Troubleshooting)

ACLAccess Control List

An ordered list of rules that permit or deny traffic or access by criteria such as address, port or user. Firewalls and routers check rules top-down, first match wins, with an implicit deny at the end; NTFS permissions are also ACLs.N10-009 4.0 (Network Security); 5.0 (Network Troubleshooting)

AHAuthentication Header

An IPsec protocol that authenticates each packet and protects its integrity but does not encrypt the payload. Because it hashes the IP header too, it fails when NAT rewrites addresses; ESP is used when confidentiality is needed.N10-009 1.0 (Networking Concepts)

APAccess Point

The device that lets wireless clients join a wired network, bridging Wi-Fi to Ethernet. Enterprise APs are often powered over PoE and managed by a controller; a rogue AP is one plugged in without authorization.N10-009 1.0 (Networking Concepts); 4.0 (Network Security)

APIApplication Programming Interface

The interface programs use to talk to each other. For an analyst, APIs are both an attack surface (broken authorization, excessive data exposure) and how tools such as SIEM, SOAR and threat intelligence platforms are wired together.N10-009 3.0 (Network Operations)

APIPAAutomatic Private Internet Protocol Addressing

The fallback that gives a Windows host a self-assigned link-local address in 169.254.0.0/16 when no DHCP server answers. Seeing a 169.254.x.x address means the client could not reach DHCP; it can talk only on the local subnet.N10-009 1.0 (Networking Concepts)

ARPAddress Resolution Protocol

The protocol that finds the MAC address belonging to a known IPv4 address on the local network, caching the answer in the ARP table (arp -a). ARP has no authentication, so attackers can spoof replies to intercept traffic; dynamic ARP inspection on switches counters this.N10-009 4.0 (Network Security)

AUPAcceptable Use Policy

The policy users accept that states what they may and may not do with company systems, networks and data.

BGPBorder Gateway Protocol

The path-vector routing protocol that connects autonomous systems and carries the internet's routing between ISPs. It runs over TCP port 179 and chooses routes by policy and AS path rather than simple metrics; inside one organization, OSPF or EIGRP is the usual choice.N10-009 2.0 (Network Implementation)

BNCBayonet Neill–Concelman

The twist-locking coaxial connector used on older 10BASE2 thinnet networks and still found on test equipment and some video gear. Its bayonet collar is what distinguishes it from the screw-on F-type connector used for cable TV and cable modems.N10-009 1.0 (Networking Concepts)

BSSIDBasic Service Set Identifier

The MAC address of a specific access point's radio, identifying one basic service set. One SSID (network name) can be served by many APs, each with its own BSSID; wireless surveys use BSSIDs to tell APs apart.N10-009 2.0 (Network Implementation)

BYODBring Your Own Device

A model where employees use personal devices for work. It raises questions of data separation, MDM enrolment and what the company may wipe.N10-009 4.0 (Network Security)

CAMContent-addressable Memory

Very fast memory that a switch searches by content rather than by address; its CAM table maps learned MAC addresses to ports. Flooding a switch with fake MACs (CAM overflow) fills the table and makes it broadcast frames like a hub.

CDNContent Delivery Network

A geographically distributed set of servers that caches web content close to users to cut latency and offload the origin server. Many CDNs also absorb DDoS traffic and terminate TLS at the provider's edge.N10-009 1.0 (Networking Concepts)

CDPCisco Discovery Protocol

Cisco's proprietary Layer 2 protocol by which neighboring devices announce their name, model, ports and IP addresses. Handy for mapping a network, but it leaks details to anyone on the segment; LLDP is the vendor-neutral equivalent.N10-009 5.0 (Network Troubleshooting)

CIAConfidentiality, Integrity, and Availability

The three core security goals: confidentiality (only authorized people see data), integrity (data is not altered undetected) and availability (systems work when needed).N10-009 4.0 (Network Security)

CIDRClassless Inter-domain Routing

The notation that writes a network's prefix length after a slash, such as 192.168.1.0/24, instead of a dotted subnet mask. It allows subnets of any size and lets routers aggregate many networks into one route (supernetting).N10-009 1.0 (Networking Concepts)

CLICommand-line Interface

A text interface where you type commands, such as the Windows Command Prompt, PowerShell, a Linux shell or a switch console. Network+ expects you to know common commands (ping, tracert/traceroute, ipconfig/ip, nslookup/dig, show commands) and when to use each.

CNAMECanonical Name

A DNS record that makes one name an alias for another, for example www.example.com pointing to example.com. The alias inherits the target's A/AAAA records; a domain's root (apex) cannot be a CNAME, and a name with a CNAME should carry no other records.N10-009 3.0 (Network Operations)

CPUCentral Processing Unit

The processor that executes instructions. On network devices, sustained high CPU from heavy traffic, routing changes or processes the device handles in software slows forwarding and management access, so CPU utilization is one of the first metrics to monitor.

CRCCyclic Redundancy Check

A checksum appended to each Ethernet frame (the frame check sequence) so the receiver can detect corruption. Rising CRC errors on a switch port usually point to a bad cable, connector, EMI or a duplex mismatch rather than a software fault.N10-009 5.0 (Network Troubleshooting)

DACDirect Attach Copper

A pre-terminated copper cable with transceivers (SFP+/QSFP) fixed to each end, used for short, cheap 10 Gbps and faster links inside a rack or between adjacent racks. Typical reach is a few meters; beyond that, use fiber.N10-009 1.0 (Networking Concepts)

DASDirect-attached Storage

Storage connected directly to one computer, such as internal SATA/NVMe drives or a USB or eSATA enclosure, with no network in between. It is fast and simple but only that host can use it; NAS and SAN share storage over a network.

DCIData Center Interconnect

The high-capacity links, often dark fiber, MPLS or DWDM, that join two or more data centers so they can replicate data, fail over and share workloads. Low latency matters because replication and clustering are sensitive to delay.N10-009 1.0 (Networking Concepts)

DDoSDistributed Denial-of-service

A denial-of-service attack launched from many sources at once, often a botnet, so blocking a single address does not stop it.N10-009 4.0 (Network Security)

DHCPDynamic Host Configuration Protocol

The protocol that automatically assigns IP addresses and network settings to devices. A rogue DHCP server can redirect traffic; DHCP snooping on switches blocks it.N10-009 1.0 (Networking Concepts); 3.0 (Network Operations); 4.0 (Network Security)

DLPData Loss Prevention

Controls that detect and block sensitive data leaving where it should stay, for example via email, uploads or USB drives.

DNSDomain Name System

The system that translates names such as example.com into IP addresses. Attacks include cache poisoning and tunnelling; DNSSEC adds signed records.N10-009 1.0 (Networking Concepts); 3.0 (Network Operations); 4.0 (Network Security)

DNSSECDomain Name System Security Extensions

Extensions that let DNS responses be digitally signed so resolvers can verify records were not forged or altered, defeating cache poisoning. It provides authenticity and integrity only; it does not encrypt queries, which is what DoT and DoH do.N10-009 3.0 (Network Operations)

DoHDNS over Hypertext Transfer Protocol Secure

DNS queries carried inside HTTPS on TCP 443, so they are encrypted and blend in with web traffic. It protects user privacy but can bypass an organization's DNS filtering and logging, which is why many enterprises block or control it.N10-009 3.0 (Network Operations)

DoSDenial-of-service

An attack that makes a service unavailable by exhausting its bandwidth, connections or resources, or by crashing it.N10-009 4.0 (Network Security)

DoTDNS over Transport Layer Security

DNS queries encrypted with TLS over a dedicated port, TCP 853. Unlike DoH it is easy to identify and manage at the firewall, while still stopping eavesdropping and tampering on the path to the resolver.N10-009 3.0 (Network Operations)

DRDisaster Recovery

Disaster recovery: the plans and processes to restore IT systems and data after a major outage, measured against RTO and RPO.N10-009 3.0 (Network Operations)

EAPoLExtensible Authentication Protocol over LAN

The framing defined by IEEE 802.1X that carries EAP authentication messages between a client (supplicant) and the switch or access point before the port is opened. The authenticator forwards them to a RADIUS server; until success, only EAPoL traffic passes.

EIGRPEnhanced Interior Gateway Routing Protocol

Cisco's advanced distance-vector routing protocol, which converges quickly and computes a composite metric from bandwidth and delay by default. It is simpler to set up than OSPF but was long Cisco-only, so mixed-vendor networks usually run OSPF.N10-009 2.0 (Network Implementation)

EOLEnd-of-life

The vendor's announcement that a product is no longer sold or developed. Devices past EOL may still work, but the next stage, end of support, means no more patches, and running them becomes a security and compliance risk.N10-009 3.0 (Network Operations)

EOSEnd-of-support

The date after which a vendor stops providing updates, security patches and technical help for a product. Any device or software past EOS should be replaced or isolated, because new vulnerabilities will never be fixed.N10-009 3.0 (Network Operations)

ESPEncapsulating Security Payload

The IPsec protocol that encrypts packet payloads and also authenticates them, providing confidentiality, integrity and anti-replay protection. It is the component used by almost every IPsec VPN; AH authenticates only and does not survive NAT.N10-009 1.0 (Networking Concepts)

ESSIDExtended Service Set Identifier

The network name shared by several access points that together form one extended service set, so clients roam between them without reconnecting. In practice it is the SSID you see in the Wi-Fi list; each AP still has its own BSSID.N10-009 2.0 (Network Implementation)

EULAEnd User License Agreement

The license contract a user accepts to install or use software. It defines what you may do (number of installs, personal vs commercial use, no reverse engineering) and makes clear that you are licensing the software, not buying it.

FCFibre Channel

A high-speed, lossless storage networking technology used to build SANs, linking servers to disk arrays over fiber with dedicated switches and host bus adapters. It delivers block-level storage; iSCSI does a similar job over ordinary Ethernet at lower cost.N10-009 1.0 (Networking Concepts)

FHRPFirst Hop Redundancy Protocol

A family of protocols (HSRP, VRRP, GLBP) that let two or more routers share one virtual IP so hosts keep a single default gateway. If the active router fails, a standby takes over the virtual address within seconds.N10-009 2.0 (Network Implementation)

FTPFile Transfer Protocol

The classic protocol for transferring files, using TCP 21 for commands and 20 for data in active mode. It sends credentials and files in cleartext, so use SFTP (over SSH, port 22) or FTPS (TLS) instead; passive mode helps through firewalls and NAT.N10-009 1.0 (Networking Concepts)

GDPRGeneral Data Protection Regulation

The European Union's data protection law, which governs how organizations anywhere handle EU residents' personal data: lawful basis, consent, breach notification within 72 hours, data subject rights and heavy fines. Network+ treats it as a key compliance driver for data handling and locality.N10-009 4.0 (Network Security)

GREGeneric Routing Encapsulation

A simple tunneling protocol (IP protocol 47) that wraps one packet inside another so traffic, including multicast and routing updates, can cross a network that would not otherwise carry it. It provides no encryption, so it is often paired with IPsec.N10-009 1.0 (Networking Concepts)

GUIGraphical User Interface

An interface of windows, icons and menus operated with a mouse or touch, as opposed to a CLI. Many switches, firewalls and access points offer a web GUI for everyday tasks, while the CLI remains faster for scripting and troubleshooting.N10-009 3.0 (Network Operations)

HTTPHypertext Transfer Protocol

The protocol browsers use to fetch web pages, on TCP port 80. It is cleartext, so anyone on the path can read or alter traffic; modern sites redirect to HTTPS, and HTTP is also a common management interface on network devices.N10-009 1.0 (Networking Concepts)

HTTPSHypertext Transfer Protocol Secure

HTTP carried inside TLS on TCP port 443, encrypting traffic and letting the browser verify the server's certificate. Certificate warnings mean the name, date or issuer did not check out; most web management consoles and cloud APIs use it.N10-009 1.0 (Networking Concepts); 3.0 (Network Operations)

IaaSInfrastructure as a Service

The cloud model where the provider supplies virtual machines, storage and networking and you install, run and patch the operating systems and software yourself, as with Amazon EC2 or Azure VMs. It gives the most control of the three models but also the most responsibility.N10-009 1.0 (Networking Concepts)

IaCInfrastructure as Code

Managing infrastructure through versioned configuration files instead of manual setup, so environments are repeatable and changes can be reviewed and scanned before deployment.N10-009 1.0 (Networking Concepts)

IAMIdentity and Access Management

Identity and access management: the processes and tools that create identities, authenticate them and control what they can access. Identity logs are a key source of indicators of compromise.N10-009 4.0 (Network Security)

ICMPInternet Control Message Protocol

The protocol that carries network diagnostics and error messages: ping uses echo request and reply, traceroute relies on time-exceeded replies, and routers send destination unreachable. Firewalls often block it, so a failed ping does not prove a host is down.N10-009 1.0 (Networking Concepts)

ICSIndustrial Control System

Industrial control systems that run physical processes in plants and utilities. Availability and safety come first, so active scanning is often restricted.N10-009 4.0 (Network Security)

IDFIntermediate Distribution Frame

A smaller wiring closet on each floor or area that terminates the horizontal cabling from nearby work areas and holds access switches. Each IDF connects back to the building's main distribution frame (MDF) over backbone cabling, usually fiber.N10-009 2.0 (Network Implementation)

IDSIntrusion Detection System

A system that monitors traffic or activity and alerts on suspected attacks without blocking them. It is passive, usually fed by a copy of the traffic.N10-009 1.0 (Networking Concepts)

IIoTIndustrial Internet of Things

Connected sensors, controllers and machines in factories, utilities and logistics, often tied to SCADA or ICS systems. These devices are long-lived, rarely patched and sometimes safety-critical, so they belong on segmented networks with strict access control.N10-009 4.0 (Network Security)

IKEInternet Key Exchange

The protocol that negotiates IPsec security associations and exchanges keys, in two phases, before ESP or AH traffic flows. It runs on UDP 500, with UDP 4500 for NAT traversal; IKEv2 is the current, simpler version.N10-009 1.0 (Networking Concepts)

IoTInternet of Things

Everyday devices with network connections: cameras, thermostats, smart speakers, light bulbs, locks. They often ship with default passwords and get few updates, so change credentials, keep firmware current and place them on a separate VLAN or guest network.N10-009 4.0 (Network Security)

IPInternet Protocol

The protocol that addresses and routes packets between networks. In logs and investigations, source and destination IP addresses are key evidence.N10-009 1.0 (Networking Concepts); 2.0 (Network Implementation); 3.0 (Network Operations); 5.0 (Network Troubleshooting)

IPAMInternet Protocol Address Management

Software that tracks which IP addresses, subnets and VLANs are allocated, free or reserved, often integrated with DHCP and DNS. It replaces the spreadsheet that goes stale and helps prevent duplicate addresses and exhausted scopes.N10-009 3.0 (Network Operations)

IPSIntrusion Prevention System

A system placed inline that inspects traffic and blocks attacks in real time. It is active, so a false positive can block legitimate traffic.N10-009 1.0 (Networking Concepts)

IPSecInternet Protocol Security

A suite that secures IP traffic at the network layer. AH provides integrity and authentication, ESP adds encryption; tunnel mode is used for site-to-site VPNs.N10-009 1.0 (Networking Concepts)

IS-ISIntermediate System to Intermediate System

A link-state interior routing protocol, like OSPF, that runs directly at Layer 2 rather than over IP and scales well in large carrier and data center networks. It is less common in enterprises; know that it is link-state and be ready to compare it with OSPF.

LACPLink Aggregation Control Protocol

The IEEE standard (802.3ad, now 802.1AX) for bundling several physical links between two devices into one logical link that adds bandwidth and survives a cable failure. Both sides must agree on settings; a mismatch leaves ports down or looping.

LANLocal Area Network

A network covering a limited area such as an office or a home, usually segmented further with VLANs.N10-009 2.0 (Network Implementation)

LCLocal Connector

A small square fiber-optic connector with a push-pull latch, half the size of SC, and the standard on SFP transceivers. It usually comes as a duplex pair for transmit and receive; keep the ends capped and clean them before plugging in.N10-009 1.0 (Networking Concepts)

LDAPLightweight Directory Access Protocol

A protocol for querying and changing directory services such as Active Directory. LDAPS protects it with TLS.N10-009 1.0 (Networking Concepts); 4.0 (Network Security)

LDAPSLightweight Directory Access Protocol over SSL

LDAP directory queries wrapped in TLS/SSL on TCP port 636, so usernames, passwords and directory data are encrypted in transit. Plain LDAP on port 389 is cleartext unless StartTLS is used, which is why directory servers should require signing or LDAPS.N10-009 1.0 (Networking Concepts)

LLDPLink Layer Discovery Protocol

The vendor-neutral IEEE 802.1AB protocol by which devices advertise their identity, port and capabilities to directly connected neighbors; LLDP-MED adds VoIP details such as the voice VLAN. It replaces Cisco's CDP in mixed networks and helps map what is plugged in where.N10-009 5.0 (Network Troubleshooting)

MACMedia Access Control

The Layer 2 addressing and access method of Ethernet and Wi-Fi. A MAC address is a 48-bit hardware identifier (the first half is the vendor OUI) that switches use to forward frames; it can be spoofed, so MAC filtering is weak security.N10-009 4.0 (Network Security)

MDFMain Distribution Frame

The main wiring room where a building's outside lines, core switches and routers terminate and where backbone cabling to each IDF begins. It is the demarcation and distribution hub, so its environment, power and access control deserve the most attention.N10-009 2.0 (Network Implementation)

MDIXMedium Dependent Interface Crossover

The port feature that detects whether the device at the other end uses the same pin layout and swaps the transmit and receive pairs internally. With auto-MDI-X, which nearly all modern gigabit ports have, you no longer need crossover cables between like devices.

MFAMultifactor Authentication

Authentication with two or more different factor types, such as something you know, have or are. Two passwords are still one factor.N10-009 4.0 (Network Security)

MIBManagement Information Base

The hierarchical database of objects (OIDs) that an SNMP-managed device exposes, such as interface counters, temperature and uptime. A monitoring system loads the vendor's MIB file so it can translate numeric OIDs into readable names and poll the right values.N10-009 3.0 (Network Operations)

MPOMultifiber Push On

A multi-fiber connector that joins 12 or 24 fibers in one rectangular plug, used for 40 and 100 Gbps links and high-density data center cabling. Polarity (which fiber lands where) and cleanliness matter more than with single-fiber connectors.N10-009 1.0 (Networking Concepts)

MTBFMean Time Between Failure

The average operating time between failures of a repairable component. A higher MTBF means more reliable hardware.N10-009 3.0 (Network Operations)

MTTRMean Time To Repair

The average time needed to repair a failed component and restore service. A lower MTTR means faster recovery.N10-009 3.0 (Network Operations)

MTUMaximum Transmission Unit

The largest packet size a link can carry; Ethernet's default is 1500 bytes. Larger packets must be fragmented or dropped, so a tunnel that adds headers can cause slow or failed transfers until the MTU is lowered or jumbo frames (up to 9000 bytes) are enabled end to end.N10-009 2.0 (Network Implementation)

MXMail Exchange

The DNS record that names the mail server or servers responsible for a domain, each with a priority value where lower is preferred. Sending servers look up the MX record to deliver mail; a missing or wrong MX means inbound email bounces.N10-009 3.0 (Network Operations)

NACNetwork Access Control

A system that checks who and what is connecting before granting network access, typically through 802.1X with a RADIUS server, and can inspect device posture (patches, antivirus). Non-compliant or unknown devices are denied or placed in a quarantine VLAN.N10-009 4.0 (Network Security)

NASNetwork-attached Storage

A dedicated storage appliance on the network that shares files over SMB or NFS, so many users and devices can reach the same folders. It works at the file level, unlike a SAN or iSCSI target that presents block storage; most include RAID and snapshots.N10-009 1.0 (Networking Concepts)

NATNetwork Address Translation

Rewrites IP addresses in packet headers as traffic crosses a router, so many hosts with private (RFC 1918) addresses share one public address. It conserves IPv4 space and hides internal addressing, but it is not a security control on its own.N10-009 1.0 (Networking Concepts); 2.0 (Network Implementation)

NFVNetwork Functions Virtualization

Running network functions such as firewalls, routers and load balancers as software on standard servers instead of dedicated appliances. Do not confuse it with SDN, which separates the control plane from the data plane; NFV virtualizes the devices themselves.N10-009 1.0 (Networking Concepts)

NICNetwork Interface Cards

The hardware that connects a device to a network. Each NIC has a MAC address.

NSName Server

A DNS record type that names the authoritative name servers for a domain or a delegated subdomain. Resolvers follow NS records from the root down to the server that holds the zone's actual A, AAAA or MX records.N10-009 3.0 (Network Operations)

NTPNetwork Time Protocol

Synchronizes device clocks with a reference time source over UDP port 123, using stratum levels (stratum 0 is the atomic or GPS clock itself). Skewed clocks break Kerberos authentication, certificate validation and log correlation.N10-009 1.0 (Networking Concepts); 3.0 (Network Operations)

NTSNetwork Time Security

An extension to NTP (RFC 8915) that uses TLS to authenticate the time server and protect packets from tampering, so an attacker in the path cannot feed clients a false time. Plain NTP is normally unauthenticated.N10-009 3.0 (Network Operations)

OSOperating System

The operating system: the core software that manages hardware and runs applications. Hardening, patching and secure configuration baselines apply to it.N10-009 3.0 (Network Operations)

OSIOpen Systems Interconnection

A seven-layer reference model for how network communication is divided: Physical, Data Link, Network, Transport, Session, Presentation, Application. Exams map devices and protocols to layers: switches at 2, routers at 3, TCP and UDP at 4, HTTP at 7.N10-009 1.0 (Networking Concepts); 5.0 (Network Troubleshooting)

OSPFOpen Shortest Path First

A link-state interior routing protocol: every router builds a complete map of its area and runs Dijkstra's algorithm to find the lowest-cost path, with cost based on bandwidth. It converges faster than RIP and scales through areas, with area 0 as the backbone.N10-009 2.0 (Network Implementation)

OTOperational Technology

Operational technology: systems that monitor and control physical processes, such as ICS and SCADA. Availability and safety usually come first, and patching is often limited.N10-009 4.0 (Network Security)

PaaSPlatform as a Service

A cloud model where the provider runs the servers, operating system and runtime, and you deploy only your application code and data. It sits between IaaS (you manage the OS) and SaaS (you manage only your data and users).N10-009 1.0 (Networking Concepts)

PATPort Address Translation

The form of NAT most home routers use: many internal hosts share one public IP, and the router tells return traffic apart by the source port it rewrote on the way out. Also called NAT overload or many-to-one NAT.N10-009 2.0 (Network Implementation)

PCI DSSPayment Card Industry Data Security Standard

The Payment Card Industry Data Security Standard: mandatory security requirements for any organization that stores, processes or transmits cardholder data, including regular vulnerability scans.N10-009 4.0 (Network Security)

PDUPower Distribution Unit

In a rack, a power strip built for data centers that distributes power to equipment, often with per-outlet monitoring or remote switching. The acronym also means Protocol Data Unit, the name for data at each OSI layer (frame, packet, segment), so read the context.N10-009 2.0 (Network Implementation)

PKIPublic Key Infrastructure

The system of certificate authorities, certificates, keys and policies that binds public keys to identities so they can be trusted.N10-009 4.0 (Network Security)

PoEPower over Ethernet

Delivers DC power over the same twisted-pair cable as Ethernet data, so access points, IP phones and cameras need no separate outlet. Standards: 802.3af (15.4 W), 802.3at PoE+ (30 W), 802.3bt (60 or 100 W). Power comes from a PoE switch or an injector.N10-009 5.0 (Network Troubleshooting)

PSKPre-shared Key

A secret shared in advance by both ends of a connection, such as the Wi-Fi passphrase in WPA2-Personal or the key for an IPsec tunnel. One key for everyone is easy to deploy but hard to revoke; enterprise networks use 802.1X instead.N10-009 2.0 (Network Implementation)

PTPPrecision Time Protocol

A time synchronization protocol (IEEE 1588) that reaches sub-microsecond accuracy, far tighter than NTP, by timestamping packets in hardware. Used in finance, telecom and industrial networks where NTP's millisecond accuracy is not enough.N10-009 3.0 (Network Operations)

PTRPointer

A reverse DNS record that maps an IP address back to a hostname, stored in the in-addr.arpa (IPv4) or ip6.arpa (IPv6) zone. Mail servers check PTR records to reject spam, so a missing or mismatched one causes delivery problems.N10-009 3.0 (Network Operations)

QoSQuality of Service

Techniques for prioritizing some traffic over the rest when a link is congested, so voice and video get low latency and jitter while bulk downloads wait. Marking uses DSCP in the IP header or CoS in the 802.1Q tag.N10-009 1.0 (Networking Concepts)

QSFPQuad Small Form-factor Pluggable

A transceiver module that carries four channels in one port, giving 40 Gbps (QSFP+) or 100 Gbps (QSFP28), used for switch uplinks and data center spine links. Transceiver type and fiber type must match at both ends.N10-009 1.0 (Networking Concepts)

RADIUSRemote Authentication Dial-in User Service

An AAA protocol that lets network devices such as wireless controllers, VPNs and switches check user credentials against a central server. UDP ports 1812 (authentication) and 1813 (accounting); it is the back end for WPA-Enterprise and 802.1X.N10-009 4.0 (Network Security)

RDPRemote Desktop Protocol

Microsoft's protocol for a remote graphical session on a Windows machine, on TCP port 3389. Never expose it directly to the internet: use a VPN or gateway, enable Network Level Authentication and restrict which accounts can connect.N10-009 1.0 (Networking Concepts)

RFIDRadio Frequency Identifier

Tags that reply with a stored identifier when energized by a reader's radio field, used in access badges, asset tracking and inventory. Passive tags need no battery. Badge cloning is a risk, so sensitive doors should use encrypted cards plus a PIN.

RIPRouting Information Protocol

A simple distance-vector routing protocol that picks paths by hop count, with a limit of 15 hops, and sends its whole table every 30 seconds. Easy to configure but slow to converge, so OSPF or EIGRP is used on anything beyond small networks.

RJRegistered Jack

A family of standardized telephone and data connectors identified by number. RJ11 is the small plug on phone and DSL lines; RJ45 is the eight-pin plug on Ethernet patch cables.N10-009 1.0 (Networking Concepts)

RPORecovery Point Objective

The maximum acceptable data loss, measured in time. An RPO of 4 hours means backups must run at least every 4 hours.N10-009 3.0 (Network Operations)

RSTPRapid Spanning Tree Protocol

The faster successor to Spanning Tree Protocol (IEEE 802.1w) that blocks redundant switch links to prevent loops and reconverges in seconds rather than up to 50. Port roles are root, designated, alternate and backup; port states are discarding, learning and forwarding, and edge ports go straight to forwarding.

RTORecovery Time Objective

The maximum acceptable time to restore a system after a disruption. It drives the choice of recovery site and method.N10-009 3.0 (Network Operations)

RXReceiver

The receive side of a link. On duplex fiber each strand carries one direction, so TX at one end must plug into RX at the other; if a link shows no light, swapping the two strands is the first fix to try.N10-009 5.0 (Network Troubleshooting)

SaaSSoftware as a Service

Software as a service: complete applications delivered over the internet. The provider runs the stack; the customer still manages data, identities and access.N10-009 1.0 (Networking Concepts)

SAMLSecurity Assertion Markup Language

An XML-based standard for exchanging authentication assertions between an identity provider and a service provider. It is common for enterprise web SSO.N10-009 4.0 (Network Security)

SANStorage Area Network

A dedicated high-speed network that gives servers block-level access to shared storage, so the storage appears as a local disk. It uses Fibre Channel or iSCSI; a NAS, by contrast, shares files over the regular network with SMB or NFS.N10-009 1.0 (Networking Concepts)

SASESecure Access Service Edge

Secure access service edge: networking (SD-WAN) and security services (SWG, CASB, ZTNA, firewall) delivered together from the cloud, close to users.N10-009 1.0 (Networking Concepts)

SCSubscriber Connector

A square push-pull fiber connector with a 2.5 mm ferrule, often seen in duplex pairs on older patch panels and ONTs. Remember the shapes: SC square, ST round bayonet, LC the smaller square used on SFP modules.N10-009 1.0 (Networking Concepts)

SCADASupervisory Control and Data Acquisition

Supervisory control and data acquisition: systems that monitor and control industrial processes across sites, such as pipelines and power grids. They are a subset of ICS.N10-009 4.0 (Network Security)

SD-WANSoftware-defined Wide Area Network

Centrally managed software that connects branch sites over whatever links are available, such as broadband, LTE and MPLS, steering each application over the best path by policy. It cuts the cost of dedicated circuits and gives one console for all sites.N10-009 1.0 (Networking Concepts)

SDNSoftware-defined Network

Software-defined networking separates the control plane from the data plane, so the network is configured centrally through software. That makes segmentation easier to automate.N10-009 1.0 (Networking Concepts)

SFPSmall Form-factor Pluggable

Small form-factor pluggable: a compact, hot-swappable transceiver for fibre or copper network ports. It is the successor to GBIC.N10-009 1.0 (Networking Concepts)

SFTPSecure File Transfer Protocol

File transfer that runs inside an SSH session on TCP port 22, encrypting both commands and data. Despite the common expansion, it is the SSH File Transfer Protocol and is unrelated to FTP; FTPS is a different protocol, FTP over TLS.N10-009 1.0 (Networking Concepts)

SIEMSecurity Information and Event Management

A system that collects and correlates logs and events from many sources to detect threats, alert and support investigations.N10-009 3.0 (Network Operations)

SIPSession Initiation Protocol

The signaling protocol that sets up, modifies and ends VoIP calls and video sessions, on port 5060 (5061 with TLS). SIP only negotiates the call; the voice itself travels in RTP streams, which is why both need QoS.N10-009 1.0 (Networking Concepts)

SLAService-level Agreement

A service-level agreement: a commitment with measurable targets, such as fixing critical vulnerabilities within 15 days. Vulnerability reports track compliance against it.N10-009 3.0 (Network Operations)

SLAACStateless Address Autoconfiguration

How an IPv6 host addresses itself without a DHCP server: it takes the network prefix from a router advertisement, builds the interface ID itself and checks for duplicates. Router advertisements can also carry DNS servers (RDNSS); otherwise DHCPv6 supplies them.N10-009 3.0 (Network Operations)

SMBServer Message Block

The Windows file and printer sharing protocol, on TCP port 445; macOS and Linux (Samba) use it to reach Windows shares too. SMBv1 is obsolete and was exploited by WannaCry, so disable it and block 445 at the perimeter.N10-009 1.0 (Networking Concepts)

SMTPSimple Mail Transfer Protocol

The protocol that sends email between mail servers and from clients to their server. Port 25 is for server-to-server relay, 587 for authenticated client submission with STARTTLS. SMTP only sends; POP3 or IMAP retrieve mail.N10-009 1.0 (Networking Concepts)

SMTPSSimple Mail Transfer Protocol Secure

SMTP wrapped in TLS from the start of the connection, usually on port 465, while port 587 normally starts in plain text and upgrades with STARTTLS. CompTIA's N10-009 objectives list SMTPS as 587, so answer 587 on this exam.N10-009 1.0 (Networking Concepts)

SNMPSimple Network Management Protocol

A protocol for monitoring and managing network devices. Use SNMPv3, which adds authentication and encryption; v1 and v2c use plaintext community strings.N10-009 1.0 (Networking Concepts); 3.0 (Network Operations)

SOAStart of Authority

The first record in every DNS zone, naming the primary name server and the administrator's email, plus the zone serial number and the refresh, retry and expire timers. Secondary servers compare the serial to decide whether to pull a zone transfer.

SQLStructured Query Language

Structured Query Language, used to query databases. SQL injection inserts attacker input into queries; parameterized queries prevent it.N10-009 1.0 (Networking Concepts)

SSESecurity Service Edge

Security service edge: cloud-delivered security services such as SWG, CASB and ZTNA. Combined with SD-WAN networking, it forms SASE.N10-009 1.0 (Networking Concepts)

SSHSecure Shell

Encrypted remote command-line access and file transfer on TCP port 22, replacing Telnet, which sends everything in plain text. Key-based authentication is stronger than passwords; disable root login and limit who may connect.N10-009 1.0 (Networking Concepts); 3.0 (Network Operations)

SSIDService Set Identifier

The name a wireless network broadcasts so clients can find and join it. Hiding the SSID is not a security measure, since it is easy to recover from client traffic; several SSIDs on one access point can map to separate VLANs for guests and staff.N10-009 2.0 (Network Implementation)

SSLSecure Socket Layer

Secure Sockets Layer, the deprecated predecessor of TLS. Finding SSL or early TLS versions enabled is a common vulnerability scan result.N10-009 1.0 (Networking Concepts)

SSOSingle Sign-on

Single sign-on: one authentication grants access to many applications. It is convenient, but it makes the identity provider a high-value target.N10-009 4.0 (Network Security)

STStraight Tip

A round fiber connector with a bayonet twist-lock and a 2.5 mm ferrule, common on older multimode installations. Remember ST as the twist-on connector; SC pushes straight in and LC is the smaller latching one.N10-009 1.0 (Networking Concepts)

STPShielded Twisted Pair

Twisted-pair cable with a foil or braid shield around the pairs to block interference, used near motors, fluorescent lights or heavy electrical equipment. The shield must be grounded to work. The same acronym also means Spanning Tree Protocol.N10-009 5.0 (Network Troubleshooting)

SVISwitch Virtual Interface

A virtual Layer 3 interface on a switch, one per VLAN, that gives the switch an IP address in that VLAN and lets a multilayer switch route between VLANs without an external router. On a Layer 2 switch it is simply the management address.N10-009 2.0 (Network Implementation)

TACACS+Terminal Access Controller Access Control System Plus

Cisco's AAA protocol for controlling administrator access to routers and switches. TCP port 49, full-packet encryption and separate authorization for individual commands make it the choice for device administration, while RADIUS handles user network access. CompTIA's list prints it as "TACAS+"; the protocol is TACACS+.N10-009 4.0 (Network Security)

TCPTransmission Control Protocol

Transmission Control Protocol: connection-oriented transport using the SYN, SYN-ACK, ACK handshake. Flags and ports in TCP traffic are key evidence in network analysis.N10-009 1.0 (Networking Concepts)

TFTPTrivial File Transfer Protocol

A bare-bones file transfer protocol over UDP port 69 with no authentication, no directory listing and no encryption. Used for pushing firmware and configurations to switches, phones and PXE boot clients; keep it on an isolated management network.N10-009 1.0 (Networking Concepts)

TTLTime to Live

A hop counter in the IP header that each router decrements; at zero the packet is discarded, which prevents endless loops. In DNS, TTL is instead how many seconds a resolver may cache a record before asking again.N10-009 1.0 (Networking Concepts)

TXTransmitter

The transmit side of a link. On duplex fiber, TX at one end must connect to RX at the other; on twisted pair, auto-MDI-X lets a straight-through cable work between like devices (switch to switch) by swapping the pairs internally.N10-009 5.0 (Network Troubleshooting)

TXTText

A DNS record holding free-form text, now used mostly for machine-readable policies: SPF rules, DKIM public keys, DMARC policy and domain ownership verification for services such as Google Workspace or Microsoft 365.N10-009 3.0 (Network Operations)

UDPUser Datagram Protocol

A connectionless transport protocol that sends datagrams without handshakes, acknowledgments or retransmission, so it is fast but unreliable. Used where speed matters more than every packet: DNS, DHCP, VoIP, streaming and TFTP.N10-009 1.0 (Networking Concepts)

UPSUninterruptible Power Supply

An uninterruptible power supply: a battery unit that keeps equipment running through short outages and allows a clean shutdown or a generator start.N10-009 2.0 (Network Implementation)

URLUniform Resource Locator

The full address of a web resource, such as https://www.example.com:443/path?query, made up of scheme, host, optional port, path and query. The scheme implies the default port (http 80, https 443) when none is given.N10-009 4.0 (Network Security)

USBUniversal Serial Bus

The standard port for peripherals and storage. Removable media can spread malware and carry data out, so it is often restricted by policy or DLP.

UTMUnified Threat Management

Unified threat management: a single appliance combining firewall, IPS, antivirus, web filtering and VPN. It is simple to run but is a single point of failure.

UTPUnshielded Twisted Pair

The common twisted-pair copper cable (Cat 5e, 6, 6A) with no shield; the pair twists alone cancel most interference. Cheap and flexible, with a 100-meter limit per run; use STP or fiber where there is heavy electrical noise.N10-009 5.0 (Network Troubleshooting)

VIPVirtual IP

An IP address not bound to one physical interface, shared by a cluster or load balancer so clients reach a service at one address while any member answers. First-hop redundancy protocols such as HSRP and VRRP give the default gateway a VIP.N10-009 2.0 (Network Implementation)

VLANVirtual Local Area Network

Splits one physical switch into separate logical networks, each its own broadcast domain, so traffic is isolated by department or device type without extra hardware. Traffic between VLANs needs a router or Layer 3 switch; 802.1Q tags carry several VLANs over a trunk.N10-009 2.0 (Network Implementation); 4.0 (Network Security); 5.0 (Network Troubleshooting)

VLSMVariable Length Subnet Mask

Using different subnet mask lengths within one network so each subnet gets only the addresses it needs: a /30 for a point-to-point link, a /24 for a user LAN. It depends on classless routing (CIDR) and cuts address waste.N10-009 1.0 (Networking Concepts)

VoIPVoice over IP

Carrying phone calls as IP packets instead of over circuit-switched lines. Calls are set up with SIP and the voice travels in RTP; they are sensitive to latency and jitter, so QoS and often a separate voice VLAN are standard.

VPCVirtual Private Cloud

A logically isolated network you define inside a public cloud, with your own address range, subnets, route tables and gateways. Security groups and network ACLs control traffic; a VPN or dedicated connection links it to the on-premises network.N10-009 1.0 (Networking Concepts)

VPNVirtual Private Network

An encrypted tunnel over an untrusted network that connects remote users or sites to a private network. It is commonly built with IPSec or TLS.N10-009 1.0 (Networking Concepts); 3.0 (Network Operations)

VXLANVirtual Extensible LAN

Encapsulates Layer 2 frames inside UDP (port 4789) so a virtual segment can stretch across routed data center networks. Its 24-bit identifier allows about 16 million segments, against 4,094 usable 802.1Q VLANs. Common in cloud and virtualized environments.N10-009 1.0 (Networking Concepts)

WANWide Area Network

A network that spans large distances and links separate sites, usually over carrier circuits or the internet. The exam contrasts it with a LAN (one site) and a MAN (one city); the router's WAN port faces the ISP.N10-009 1.0 (Networking Concepts)

WPAWi-Fi Protected Access

The family of Wi-Fi security standards. Original WPA with TKIP was a stopgap after WEP and is now weak; WPA2 brought AES-CCMP; WPA3 adds SAE to resist offline password cracking. Personal uses a shared passphrase, Enterprise authenticates each user via RADIUS.N10-009 2.0 (Network Implementation)

WPSWi-Fi Protected Setup

A convenience feature that joins a device to Wi-Fi with a button press or an eight-digit PIN instead of the passphrase. The PIN method can be brute-forced in hours because it is validated in two halves, so WPS should be disabled.

ZTAZero Trust Architecture

A security model that trusts nothing by network location: every request is authenticated, authorized and encrypted, whether it comes from inside or outside. Core ideas are least privilege, continuous verification and separating the policy decision point from the enforcement point.N10-009 1.0 (Networking Concepts)

Acronyms and expansions from the CompTIA Network+ N10-009 exam objectives (v4.0) (acronym list), checked 2 November 2026. Definitions are CertSprint's own.