CompTIA Network+ N10-009

CompTIA Network+ N10-009 Flashcards: 434 cards

434 free CompTIA Network+ flashcards from the course's cheat sheet and glossary. Tap a card to flip it. Mark the ones you know and they drop out of the deck; the rest keep coming back.

Acronyms 316

1000BASE-LX: Gigabit Ethernet, long wavelength. 1 Gbps over single-mode fiber to 10 km (also works on multimode for short runs).
1000BASE-SX: Gigabit Ethernet, short wavelength. 1 Gbps over multimode fiber to about 550 m.
1000BASE-T: Gigabit Ethernet over twisted pair. 1 Gbps over Cat 5e or better to 100 m, using all four pairs.
100BASE-TX: Fast Ethernet over twisted pair. 100 Mbps over Cat 5 or better using two pairs.
10BASE-T: Ethernet over twisted pair. The original 10 Mbps twisted-pair Ethernet.
10GBASE-ER: 10 Gigabit Ethernet, extended reach. 10 Gbps over single-mode fiber to 40 km.
10GBASE-LR: 10 Gigabit Ethernet, long reach. 10 Gbps over single-mode fiber to 10 km.
10GBASE-SR: 10 Gigabit Ethernet, short reach. 10 Gbps over multimode fiber, about 300 m on OM3, 400 m on OM4.
10GBASE-T: 10 Gigabit Ethernet over twisted pair. 10 Gbps over Cat 6A to 100 m (Cat 6 to 55 m).
40GBASE-T: 40 Gigabit Ethernet over twisted pair. 40 Gbps over Cat 8 to 30 m.
4G: Fourth-generation cellular. The LTE generation of mobile broadband.
5G: Fifth-generation cellular. The current mobile network generation with higher speed and lower latency than LTE.
802.11: IEEE 802.11. The family of Wi-Fi standards.
802.1AX: IEEE 802.1AX. The current standard for link aggregation, using LACP.
802.1D: IEEE 802.1D. The original spanning tree standard.
802.1Q: IEEE 802.1Q. The VLAN tagging standard: a 4-byte tag in the Ethernet frame carries the VLAN ID on trunks.
802.1s: IEEE 802.1s. Multiple Spanning Tree Protocol.
802.1w: IEEE 802.1w. Rapid Spanning Tree Protocol.
802.1X: IEEE 802.1X. Port-based network access control: a device must authenticate before the switch port or Wi-Fi passes traffic.
802.3ad: IEEE 802.3ad. The original link aggregation standard, now part of 802.1AX.
802.3af: IEEE 802.3af. The original Power over Ethernet standard: about 15.4 W at the switch, 12.95 W at the device.
802.3at: IEEE 802.3at. PoE+: about 30 W at the switch, 25.5 W at the device.
802.3bt: IEEE 802.3bt. PoE++: 60 W (Type 3) or up to 90 W (Type 4) using all four pairs.
8P8C: Eight position, eight contact. The formal name of the connector everyone calls RJ45.
AAA: Authentication, authorization, and accounting. Prove who you are, decide what you may do, record what you did.
AAAA: Quad-A record. The DNS record that maps a name to an IPv6 address.
ACK: Acknowledgment. The TCP flag or message confirming data arrived.
ACL: Access control list. An ordered list of permit and deny rules on a router, firewall, or file system.
AD: Administrative distance. A router's trust ranking for route sources; the lowest wins when two protocols offer the same prefix.
AES: Advanced Encryption Standard. The standard symmetric cipher, with 128, 192, or 256-bit keys.
AH: Authentication Header. The IPsec protocol that provides integrity and authentication without encryption.
AP: Access point. The radio that bridges Wi-Fi clients onto the wired network.
APC: Angled physical contact. A fiber connector polish with an 8-degree angle (green) that reflects less light.
API: Application programming interface. The defined way one program talks to another, such as the web endpoints a cloud service exposes.
APIPA: Automatic Private IP Addressing. The 169.254.x.x address a host gives itself when it cannot reach a DHCP server.
ARP: Address Resolution Protocol. Finds the MAC address that goes with a known IPv4 address on the local segment.
AS: Autonomous system. A network under one administration with its own routing policy, identified by a number for BGP.
ASCII: American Standard Code for Information Interchange. The character encoding that maps letters and symbols to numbers 0 to 127.
AUP: Acceptable use policy. The rules for how staff may use company systems and data.
BASE: Baseband. The middle of Ethernet names: the cable carries one digital signal at a time.
BGP: Border Gateway Protocol. The path-vector routing protocol of the internet, between autonomous systems.
BNC: Bayonet Neill-Concelman connector. The twist-lock coax connector used on older LANs, test equipment, and CCTV.
BPDU: Bridge protocol data unit. The frames switches exchange to build the spanning tree.
BSSID: Basic service set identifier. The MAC address of one access point radio, which identifies that specific cell.
BYOD: Bring your own device. Staff use personal phones and laptops for work.
CA: Certificate authority. The trusted entity that signs certificates.
CAM: Content-addressable memory (table). The switch's MAC address table.
CAN: Campus area network. A network spanning several buildings on one campus.
CASB: Cloud access security broker. Sits between users and cloud apps to enforce policy, visibility, and data protection.
CCMP: Counter Mode with Cipher Block Chaining Message Authentication Code Protocol. The AES-based encryption WPA2 uses.
CDN: Content delivery network. Caches content on servers around the world so users fetch it from nearby.
CDP: Cisco Discovery Protocol. Cisco's Layer 2 protocol for learning what device is on the other end of a link.
CIA: Confidentiality, integrity, and availability. The three goals of security: keep data secret, keep it correct, keep it reachable.
CIDR: Classless inter-domain routing. Prefix notation for subnets, such as /24, replacing the old A, B, C classes.
CNAME: Canonical name record. A DNS alias: one name points to another name.
CPU: Central processing unit. The processor that executes instructions.
CRC: Cyclic redundancy check. The checksum in an Ethernet frame trailer; CRC errors mean the frame was damaged in transit.
CRM: Customer relationship management. Software for tracking customers and sales, usually SaaS.
CSMA/CD: Carrier sense multiple access with collision detection. The original Ethernet rule: listen before sending, and back off if a collision is heard.
DaaS: Desktop as a service. VDI hosted by a cloud provider.
DAC: Direct attach cable. A twinaxial copper cable with transceivers permanently attached at both ends, for short 10 to 100 Gbps links.
DDoS: Distributed denial of service. Many sources, usually a botnet, flood a target at once.
DFS: Dynamic frequency selection. Wi-Fi channels in the 5 GHz band that must yield to radar.
DHCP: Dynamic Host Configuration Protocol. Hands out IP addresses, masks, gateways, and DNS servers automatically (UDP 67 and 68).
DKIM: DomainKeys Identified Mail. Outgoing mail is digitally signed; the public key is published in DNS.
DMARC: Domain-based Message Authentication, Reporting, and Conformance. A DNS policy telling receivers what to do with mail that fails SPF or DKIM, and where to send reports.
DMZ: Demilitarized zone. A screened subnet between the internet and the internal network for public-facing servers.
DNS: Domain Name System. Translates names such as www.example.com into IP addresses (UDP 53, TCP 53 for zone transfers).
DNS64: DNS 6 to 4. Synthesizes AAAA records for IPv4-only names so IPv6-only clients can reach them through NAT64.
DNSSEC: DNS Security Extensions. Digital signatures on DNS records so a resolver can tell an answer was not forged.
DoH: DNS over HTTPS. DNS queries carried inside HTTPS on TCP 443 so they cannot be read or altered in transit.
DORA: Discover, Offer, Request, Acknowledge. The four-step DHCP lease exchange.
DoS: Denial of service. One source floods or crashes a target so it cannot serve users.
DoT: DNS over TLS. DNS queries encrypted with TLS on TCP 853.
DR: Disaster recovery. The plans and sites for restoring IT after a major outage.
DSS: Data Security Standard. The PCI DSS rules for protecting payment card data.
EGP: Exterior gateway protocol. A routing protocol between organizations; today that means BGP.
EIGRP: Enhanced Interior Gateway Routing Protocol. Cisco's advanced distance-vector protocol with fast convergence and a composite metric.
EMI: Electromagnetic interference. Noise from motors, power lines, fluorescent lights, and radios that corrupts signals on copper cable.
EOL: End of life. The vendor stops selling the product.
EOS: End of support. The vendor stops providing patches and help.
ER: Extended reach. The single-mode 10 Gbps optic for 40 km.
ESP: Encapsulating Security Payload. The IPsec protocol that encrypts and authenticates the payload.
ESSID: Extended service set identifier. The SSID shared by several access points so clients can roam between them.
EU: European Union. The political union whose GDPR privacy law reaches any company holding its residents' data.
EUI-64: Extended unique identifier, 64-bit. A way to build an IPv6 interface ID from a 48-bit MAC address.
FCC: Federal Communications Commission. The US regulator of radio spectrum, including Wi-Fi bands and transmit power.
FHRP: First-hop redundancy protocol. Lets two routers share one virtual gateway address so hosts keep working if one fails.
FIN: Finish flag. The TCP flag that closes a connection gracefully.
FTP: File Transfer Protocol. Plaintext file transfer on TCP 21 (control) and 20 (data); replace with SFTP or FTPS.
FTPS: FTP Secure. FTP wrapped in TLS, ports 990 and 989 (implicit) or 21 with an upgrade (explicit).
GBIC: Gigabit interface converter. The older, larger hot-swappable transceiver replaced by the SFP.
Gbps: Gigabits per second. Billions of bits per second; gigabit Ethernet is 1 Gbps.
GDPR: General Data Protection Regulation. The European Union's privacy law for personal data of EU residents.
GG45: GG45 connector. A backward-compatible Cat 7 and Cat 8 connector that also accepts RJ45 plugs.
GHz: Gigahertz. Billions of cycles per second; CPU clock speed and Wi-Fi band frequency.
GLBP: Gateway Load Balancing Protocol. Cisco's first-hop redundancy that also spreads traffic across several gateways.
GPS: Global Positioning System. Satellite positioning, also used as a stratum 0 time reference.
GRE: Generic Routing Encapsulation. A simple tunnel that wraps one packet inside another, with no encryption.
GUI: Graphical user interface. Windows, icons, and a mouse, as opposed to a command line.
HIPAA: Health Insurance Portability and Accountability Act. The US law protecting health information and setting privacy and security rules.
HSRP: Hot Standby Router Protocol. Cisco's first-hop redundancy protocol: one active router, one standby, one virtual IP.
HTTP: Hypertext Transfer Protocol. Web traffic in the clear on TCP 80.
HTTPS: Hypertext Transfer Protocol Secure. HTTP inside TLS on TCP 443.
IaaS: Infrastructure as a service. The provider supplies virtual machines, storage, and networks; you manage the operating system and up.
IaC: Infrastructure as code. Defining networks and servers in files that tools build automatically and repeatably.
IBSS: Independent basic service set. An ad hoc Wi-Fi network between devices with no access point.
ICMP: Internet Control Message Protocol. The messaging protocol behind ping and traceroute, and behind unreachable and time-exceeded errors.
ICS: Industrial control system. The general term for computers that run physical processes; SCADA is one kind.
ID: Identifier or identification. A name or number that uniquely labels a user, device, session, or record.
IDF: Intermediate distribution frame. A smaller wiring closet on a floor or wing that feeds back to the MDF.
IDS: Intrusion detection system. Watches a copy of the traffic and alerts on attacks; cannot block them.
IEEE: Institute of Electrical and Electronics Engineers. The engineering body behind Ethernet (802.3), Wi-Fi (802.11), and many device standards.
IGMP: Internet Group Management Protocol. How hosts join and leave IPv4 multicast groups.
IGP: Interior gateway protocol. A routing protocol used inside one organization: OSPF, EIGRP, RIP, IS-IS.
IIoT: Industrial Internet of Things. Networked sensors and controllers in factories and utilities.
IKE: Internet Key Exchange. Negotiates the keys and security associations for IPsec; UDP 500, and 4500 through NAT.
IMAP: Internet Message Access Protocol. Reads mail that stays on the server, synced across devices; TCP 143, secure 993.
IMAPS: IMAP Secure. IMAP over TLS on TCP 993.
IoT: Internet of Things. Networked devices such as cameras, sensors, thermostats, and smart TVs.
IP: Internet Protocol. The Layer 3 protocol that addresses and routes packets between networks.
IPAM: IP address management. Software that tracks which addresses and subnets are in use.
IPFIX: IP Flow Information Export. The standard flow-export protocol, the successor of NetFlow.
IPS: Intrusion prevention system. Sits inline and blocks attacks as they pass.
IPsec: Internet Protocol Security. The suite that encrypts and authenticates IP packets for VPNs.
IPv4: Internet Protocol version 4. 32-bit addresses written as four decimal octets, such as 192.168.1.10.
IPv6: Internet Protocol version 6. 128-bit addresses in eight hex groups; no broadcast, built-in autoconfiguration.
IS-IS: Intermediate System to Intermediate System. A link-state interior routing protocol used mainly by large providers.
ISATAP: Intra-Site Automatic Tunnel Addressing Protocol. A tunneling method that carries IPv6 inside IPv4 within one organization.
iSCSI: Internet SCSI. SCSI storage commands over a TCP/IP network, giving block-level storage without Fibre Channel.
ISP: Internet service provider. The company that connects you to the internet.
IT: Information technology. Computers, networks, and the people who run them.
JPEG: Joint Photographic Experts Group (image format). The common compressed photo format.
LACP: Link Aggregation Control Protocol. Negotiates bundling several physical links into one logical link (802.1AX, formerly 802.3ad).
LAN: Local area network. One site's network: a building, floor, or campus that one organization owns and runs.
LC: Lucent connector. The small square snap-in fiber connector, the most common on modern transceivers.
LDAP: Lightweight Directory Access Protocol. Queries a directory such as Active Directory for users and groups; TCP 389, secure 636.
LDAPS: LDAP Secure. LDAP over TLS on TCP 636.
LED: Light-emitting diode. A small light source: the status lights on a port, the lamp in cheap fiber transmitters, and modern display backlights.
LLC: Logical link control. The upper sublayer of the data link layer that identifies which network protocol a frame carries.
LLDP: Link Layer Discovery Protocol. The vendor-neutral neighbor discovery protocol (IEEE 802.1AB).
LR: Long reach. The single-mode 10 Gbps optic, 10 km.
LTE: Long-Term Evolution. 4G cellular data; the workhorse mobile broadband standard.
MAC: Media access control (address). The 48-bit hardware address burned into a network interface, used at Layer 2.
macOS: Mac operating system. Apple's desktop operating system.
MAN: Metropolitan area network. A city-sized network: bigger than a LAN, smaller than a WAN.
Mbps: Megabits per second. Millions of bits per second; the unit for network link speed.
MDF: Main distribution frame. The building's main wiring closet where outside lines and the core equipment land.
MDIX: Medium-dependent interface crossover. Auto-MDIX ports sense the cable and swap transmit and receive pairs, so crossover cables are rarely needed.
MFA: Multi-factor authentication. Two or more different kinds of proof: something you know, have, are, or where you are.
MHz: Megahertz. Millions of cycles per second; memory speed, radio channels, and older CPU clocks.
MIB: Management information base. The database of variables an SNMP agent exposes.
MIMO: Multiple input, multiple output. Using several antennas at once to send parallel data streams for more speed.
MMF: Multimode fiber. A wider core (50 or 62.5 microns) carrying many light paths, for hundreds of meters.
MOU: Memorandum of understanding. A non-binding statement of intent and roles between parties.
MPEG: Moving Picture Experts Group (video format). The family of compressed video formats.
MPLS: Multiprotocol Label Switching. A provider WAN that forwards by short labels instead of IP lookups, with traffic engineering and QoS.
MPO: Multi-fiber push-on connector. A ribbon connector carrying 12 or 24 fibers, used for 40 and 100 Gbps parallel optics.
ms: Millisecond. One thousandth of a second; latency and response times.
MSTP: Multiple Spanning Tree Protocol. Runs one spanning tree instance for a group of VLANs instead of one per VLAN.
MTBF: Mean time between failures. The average running time before a component fails; a reliability measure.
MTP: Multi-fiber termination push-on connector. A brand-name, higher-precision version of the MPO connector.
MTTR: Mean time to repair. The average time to fix a failure and restore service.
MTU: Maximum transmission unit. The largest packet a link can carry, 1500 bytes on standard Ethernet.
MU-MIMO: Multi-user MIMO. The access point serves several clients at the same time with separate streams.
MX: Mail exchanger record. The DNS record that says which server accepts email for a domain.
NAC: Network access control. Checks a device's identity and health before letting it onto the network.
NACL: Network access control list. A stateless rule set applied to a cloud subnet.
NAS: Network-attached storage. A file server appliance that shares folders over the regular network using SMB or NFS.
NAT: Network address translation. Rewrites private inside addresses to a public address at the router so many hosts can share it.
NAT-T: NAT traversal. Wraps IPsec in UDP 4500 so it can pass through address translation.
NAT64: Network address translation 6 to 4. Lets IPv6-only hosts reach IPv4-only servers by translating between the two.
NDA: Non-disclosure agreement. A contract that keeps shared information confidential.
NDP: Neighbor Discovery Protocol. IPv6's replacement for ARP: finds neighbors' MAC addresses and routers using ICMPv6.
NFS: Network File System. The Unix and Linux file-sharing protocol.
NFV: Network functions virtualization. Running routers, firewalls, and load balancers as virtual machines instead of dedicated hardware.
NIC: Network interface card. The adapter that connects a computer to the network, wired or wireless.
NS: Name server record. The DNS record listing the authoritative name servers for a zone.
NTP: Network Time Protocol. Synchronizes clocks across the network (UDP 123); wrong time breaks Kerberos, certificates, and logs.
NTS: Network Time Security. Authentication and integrity for NTP so time cannot be spoofed.
OFDM: Orthogonal frequency-division multiplexing. The modulation that sends data across many closely spaced sub-carriers at once.
OFDMA: Orthogonal frequency-division multiple access. Wi-Fi 6 splits a channel into small sub-channels so many clients share it efficiently.
OID: Object identifier. The dotted number that names one value in an SNMP MIB.
OM1: Optical multimode 1. 62.5 micron multimode fiber, orange, the oldest grade.
OM2: Optical multimode 2. 50 micron multimode fiber, orange, 1 Gbps to about 550 m.
OM3: Optical multimode 3. Laser-optimized 50 micron multimode fiber, aqua, 10 Gbps to about 300 m.
OM4: Optical multimode 4. Higher-bandwidth 50 micron multimode fiber, aqua, 10 Gbps to about 400 m.
OS: Operating system. The software that manages hardware and runs applications: Windows, macOS, Linux, iOS, Android.
OSFP: Octal small form-factor pluggable. An eight-lane 400 Gbps module, slightly larger than QSFP-DD.
OSI: Open Systems Interconnection model. The seven-layer reference model used to describe where a protocol or device does its work.
OSPF: Open Shortest Path First. A link-state interior routing protocol that uses cost (bandwidth) as its metric and converges fast.
OT: Operational technology. Hardware and software that controls physical equipment, as opposed to IT.
OTDR: Optical time-domain reflectometer. A fiber tester that sends light pulses and measures reflections to find breaks and their distance.
OUI: Organizationally unique identifier. The first 24 bits of a MAC address, which identify the manufacturer.
PaaS: Platform as a service. The provider runs the platform (OS, runtime, database); you deploy code.
PAN: Personal area network. A network within arm's reach, such as Bluetooth between a phone and earbuds.
PAT: Port address translation. Many inside hosts share one public IP address, told apart by port numbers.
PC: Personal computer. A desktop or laptop for one user.
PCI: Payment Card Industry. The card brands' rules (PCI DSS) for anyone who stores, processes, or transmits payment card data.
PDU: Protocol data unit. The name of the chunk of data at each layer: bits, frames, packets, segments or datagrams, data.
PIN: Personal identification number. A short numeric secret, a something-you-know factor.
PKI: Public key infrastructure. The system of certificate authorities, certificates, and revocation that makes public keys trustworthy.
PoE: Power over Ethernet. Delivers DC power to devices over the data cable: 802.3af 15.4 W, 802.3at 30 W, 802.3bt 60 to 90 W.
PON: Passive optical network. Fiber to the premises using unpowered splitters between the provider and many customers.
POP3: Post Office Protocol version 3. Downloads mail to one device and usually deletes it from the server; TCP 110, secure 995.
POP3S: POP3 Secure. POP3 over TLS on TCP 995.
PSK: Pre-shared key. One shared passphrase for everyone on a Wi-Fi network (Personal mode).
PTP: Precision Time Protocol. IEEE 1588 clock sync with sub-microsecond accuracy, for finance, telecom, and industrial systems.
PTR: Pointer record. The reverse DNS record: IP address back to a name.
PVC: Polyvinyl chloride. The ordinary cable jacket, which gives off toxic smoke; plenum cable is required in air spaces.
QSFP: Quad small form-factor pluggable. A four-lane module for 40 Gbps.
QSFP-DD: Quad small form-factor pluggable double density. Eight lanes for 400 Gbps.
QSFP+: Quad small form-factor pluggable plus. Four 10 Gbps lanes: a 40 Gbps module.
QSFP28: Quad small form-factor pluggable 28. Four 25 Gbps lanes: a 100 Gbps module.
RA: Router advertisement. The IPv6 message a router sends with the prefix and gateway information hosts use for SLAAC.
RADIUS: Remote Authentication Dial-In User Service. The AAA server behind Wi-Fi Enterprise, VPNs, and 802.1X; UDP 1812 and 1813.
RARP: Reverse Address Resolution Protocol. An obsolete protocol for finding an IP address from a MAC address.
RBAC: Role-based access control. Permissions are assigned to roles, and users get roles.
RC4: Rivest Cipher 4. A fast stream cipher used in WEP and old TLS; broken and deprecated.
RDP: Remote Desktop Protocol. Microsoft's remote graphical desktop on TCP 3389.
RF: Radio frequency. Radio signals; the medium of Wi-Fi, cellular, and Bluetooth, and a source of interference and, in medicine, surgical energy.
RFC: Request for Comments. The numbered documents that define internet standards, such as RFC 1918 private addresses.
RFI: Radio frequency interference. Electromagnetic interference in the radio bands, from transmitters, microwaves, and other radios.
RG-59: Radio Guide 59 coaxial cable. Thinner coax for short runs such as CCTV, often with a BNC connector.
RG-6: Radio Guide 6 coaxial cable. The modern coax grade for cable TV and cable modems, with an F-type connector.
RIP: Routing Information Protocol. The classic distance-vector protocol: hop count metric, 15-hop limit, slow.
RJ11: Registered jack 11. The small telephone plug, used for analog phone lines and DSL.
RJ45: Registered jack 45. The eight-pin plug on Ethernet twisted-pair cables (properly an 8P8C connector).
RPC: Remote procedure call. A program calls a function on another computer as if it were local.
RPO: Recovery point objective. The maximum acceptable data loss, measured in time.
RST: Reset flag. The TCP flag that aborts a connection immediately.
RSTP: Rapid Spanning Tree Protocol. The faster version of spanning tree (802.1w) that reconverges in seconds.
RTO: Recovery time objective. The maximum acceptable time to restore a service after failure.
RX: Receive. The receiving side of a link or the receiving fiber strand.
SaaS: Software as a service. Complete applications delivered over the web, such as email and office suites.
SAE: Simultaneous authentication of equals. The WPA3 Personal handshake that resists offline password guessing.
SAML: Security Assertion Markup Language. An XML standard for passing authentication between an identity provider and a web application (enterprise SSO).
SAN: Storage area network. A dedicated network that gives servers block-level access to shared disk arrays.
SASE: Secure access service edge. SD-WAN networking plus cloud-delivered security (firewall, web gateway, ZTNA, CASB) as one service.
SC: Subscriber connector. The larger square push-pull fiber connector, common on older gear and patch panels.
SCADA: Supervisory control and data acquisition. Systems that monitor and control industrial processes such as power, water, and manufacturing.
SCP: Secure Copy Protocol. Simple file copying over SSH, TCP 22.
SD-WAN: Software-defined wide area network. Steers traffic across several cheap links (broadband, LTE, MPLS) by policy from a central controller.
SDN: Software-defined networking. Separates the control plane (decisions) from the data plane (forwarding) and centralizes control.
SFP: Small form-factor pluggable transceiver. The hot-swappable module that gives a switch port its fiber or copper interface, 1 Gbps.
SFP+: Enhanced small form-factor pluggable. The 10 Gbps version of the SFP module.
SFTP: SSH File Transfer Protocol. File transfer inside an SSH session, TCP 22.
SHA-256: Secure Hash Algorithm 256-bit. The standard hash today: a 256-bit fingerprint of any input.
SIEM: Security information and event management. Collects logs from everything, correlates them, and raises alerts.
SIP: Session Initiation Protocol. Sets up and tears down voice and video calls; port 5060, or 5061 with TLS.
SLA: Service level agreement. The contract stating measurable service commitments, such as 99.9% uptime.
SLAAC: Stateless address autoconfiguration. IPv6 hosts build their own address from the router's advertised prefix, no DHCP server needed.
SMB: Server Message Block. Windows file and printer sharing on TCP 445.
SMF: Single-mode fiber. A tiny core (about 9 microns) and a laser, for long distances.
SMTP: Simple Mail Transfer Protocol. Sends email between servers on TCP 25; clients submit on 587 with TLS.
SMTPS: SMTP Secure. SMTP with TLS, port 465 (implicit) or 587 with STARTTLS.
SNMP: Simple Network Management Protocol. Polls and receives alerts from network devices (UDP 161 polls, 162 traps).
SNTP: Simple Network Time Protocol. A lighter version of NTP for clients that need less accuracy.
SOA: Start of authority record. The record at the top of a DNS zone: primary server, contact, serial number, and timers.
SOX: Sarbanes-Oxley Act. The US law requiring accurate financial reporting and controls, with IT audit implications.
SPAN: Switched port analyzer. A switch feature that mirrors traffic from ports or VLANs to a monitoring port.
SPF: Sender Policy Framework. A DNS TXT record listing which servers may send mail for a domain.
SQL: Structured Query Language. The language used to query databases; also the name of the servers on TCP 1433 (Microsoft) and 3306 (MySQL).
SR: Short reach. The multimode 10 Gbps optic, about 300 m on OM3.
SRV: Service record. A DNS record that locates a service: host, port, priority, and weight.
SSE: Security service edge. The security half of SASE: secure web gateway, CASB, zero trust access, delivered from the cloud.
SSH: Secure Shell. Encrypted remote command-line access and file transfer on TCP 22; replaces Telnet and FTP.
SSID: Service set identifier. The Wi-Fi network name that access points broadcast and clients join.
SSO: Single sign-on. Log in once and reach many systems without signing in again.
ST: Straight tip connector. The round bayonet twist-lock fiber connector; legacy.
STP: Spanning Tree Protocol. Blocks redundant switch links so frames cannot loop, while keeping them ready as backups. Also: Shielded twisted pair. Twisted-pair cable with foil or braid around the pairs for noisy environments; the shield must be grounded.
SVI: Switch virtual interface. A virtual Layer 3 interface on a switch that gives a VLAN an IP address and routes for it.
SYN: Synchronize flag. The first packet of a TCP handshake.
Syslog: System logging protocol. Sends device log messages to a central server on UDP 514 with severity levels 0 to 7.
T568A: TIA/EIA 568A wiring standard. One of the two pin-outs for RJ45 cables; green pair on pins 1 and 2.
T568B: TIA/EIA 568B wiring standard. The more common RJ45 pin-out; orange pair on pins 1 and 2.
TACACS+: Terminal Access Controller Access-Control System Plus. Cisco's AAA protocol for device administration on TCP 49; encrypts the whole payload and separates authentication from authorization.
TCP: Transmission Control Protocol. Reliable, ordered, connection-based transport: three-way handshake, acknowledgments, retransmission.
TERA: TERA connector. A shielded, non-RJ45 connector used with Cat 7 cabling.
TFTP: Trivial File Transfer Protocol. Bare-bones UDP 69 file transfer with no login, used for firmware and config files.
TKIP: Temporal Key Integrity Protocol. WPA's per-packet keying scheme; deprecated.
TLS: Transport Layer Security. The encryption layer under HTTPS and most secure protocols; use 1.2 or 1.3.
TOTP: Time-based one-time password. A six-digit code from an authenticator app that changes every 30 seconds.
TTL: Time to live. A counter that keeps packets and DNS records from living forever.
TV: Television. A display or broadcast receiver; smart TVs are IoT devices.
TX: Transmit. The sending side of a link or the sending fiber strand.
TXT: Text record. A free-text DNS record, used for SPF, DKIM, DMARC, and domain ownership checks.
UDP: User Datagram Protocol. Connectionless, fast transport with no delivery guarantee; used for voice, video, DNS, DHCP.
UPC: Ultra physical contact. The flat, blue fiber connector polish used in most LANs.
UPS: Uninterruptible power supply. A battery unit that keeps equipment running through a power cut and conditions the power.
URL: Uniform resource locator. A web address such as https://www.example.com/page.
US: United States. The country; US standards, 60 Hz mains, and US connector conventions.
USB: Universal Serial Bus. The standard port for peripherals, storage, and charging.
UTP: Unshielded twisted pair. The standard copper network cable: four twisted pairs, no shield.
VA: Volt-ampere. The unit of apparent power used to size a UPS.
VCSEL: Vertical-cavity surface-emitting laser. The cheap laser used in multimode fiber transceivers.
VFL: Visual fault locator. A visible red laser that lights up a fiber so you can see breaks and trace strands.
VLAN: Virtual local area network. A logical LAN on a switch: ports in different VLANs are separate broadcast domains.
VLSM: Variable-length subnet masking. Using different subnet sizes inside one network so addresses are not wasted.
VM: Virtual machine. A complete computer running as software on a hypervisor.
VNI: VXLAN network identifier. The 24-bit segment ID in a VXLAN header.
VoIP: Voice over IP. Telephone calls carried as packets on the data network.
VPC: Virtual private cloud. Your isolated virtual network inside a cloud provider.
VPN: Virtual private network. An encrypted tunnel across an untrusted network such as the internet.
VRRP: Virtual Router Redundancy Protocol. The open-standard first-hop redundancy protocol.
VTP: VLAN Trunking Protocol. Cisco's protocol for distributing VLAN definitions to other switches.
VXLAN: Virtual extensible LAN. Tunnels Layer 2 segments over a Layer 3 network with a 24-bit ID, giving 16 million segments instead of 4094 VLANs.
WAN: Wide area network. Connects LANs across cities or countries, usually over links leased from a provider.
WEP: Wired Equivalent Privacy. The original Wi-Fi encryption, broken in minutes; never use it.
Wi-Fi: Wireless fidelity. The trade name for IEEE 802.11 wireless networking.
WLAN: Wireless local area network. A LAN delivered over Wi-Fi instead of cables.
WLC: Wireless LAN controller. A central device that configures and manages many lightweight access points.
WPA: Wi-Fi Protected Access. The interim fix for WEP that used TKIP; deprecated.
WPA2: Wi-Fi Protected Access 2. Wi-Fi security using AES with CCMP; still common and acceptable.
WPA3: Wi-Fi Protected Access 3. The current Wi-Fi security standard: SAE in Personal mode, stronger encryption, protected management frames.
ZTNA: Zero trust network access. Every request is authenticated and authorized, regardless of where it comes from.

The exam itself 9

Exam code: N10-009 (Network+)
Questions: Up to 90, multiple choice plus performance-based
Time: 90 minutes
Passing score: 720 on a scale of 100 to 900 (about 72%)
1.0 Networking Concepts: 23%
2.0 Network Implementation: 20%
3.0 Network Operations: 19%
4.0 Network Security: 14%
5.0 Network Troubleshooting: 24%

IPv4 addressing and subnetting 7

10.0.0.0/8 (10.0.0.0 to 10.255.255.255): Private, RFC 1918
172.16.0.0/12 (172.16.0.0 to 172.31.255.255): Private, RFC 1918. 172.32.x.x is public
192.168.0.0/16 (192.168.0.0 to 192.168.255.255): Private, RFC 1918
169.254.0.0/16: APIPA, link-local. Means DHCP failed
255.255.255.255: Limited broadcast (DHCP Discover)
0.0.0.0/0: Default route, route of last resort
100.64.0.0/10: Carrier-grade NAT shared space

Switching 10

Standard: STP 802.1D; RSTP 802.1w; MSTP 802.1s
Root bridge: Lowest bridge ID (priority then MAC). Set core priority low
Port roles: Root port (toward root), designated port (one per link), blocked (redundant). RSTP adds alternate and backup
STP states: Blocking, listening, learning, forwarding: 30 to 50 seconds
RSTP states: Discarding, learning, forwarding: converges in seconds
PortFast: Skips listening and learning on host ports. Never on switch-to-switch links
BPDU guard: Shuts a PortFast port that receives a BPDU (rogue switch)
Root guard: Stops a downstream switch from becoming root
Loop guard: Protects against unidirectional link failures
Loop symptoms: Broadcast storm, CPU at 100 percent, MAC addresses flapping, everything slow after adding a redundant cable

Routing, NAT, and gateway redundancy 8

Directly connected: 0
Static: 1
External BGP: 20
EIGRP: 90
OSPF: 110
IS-IS: 115
RIP: 120
Internal BGP: 200

DHCP, DNS, and time 9

A: Name to IPv4 address
AAAA: Name to IPv6 address
CNAME: Alias: one name to another name
MX: Mail exchanger for the domain, with priority
NS: Authoritative name servers for a zone
SOA: Start of authority: zone serial and timers
PTR: IP address back to a name (reverse zone, in-addr.arpa)
TXT: Free text: SPF, DKIM, DMARC, domain verification
SRV: Locates a service by name, port, and priority (SIP, Active Directory)

Network operations 18

SNMP: Agent on the device, MIB database, OID per variable. Manager polls with Get on UDP 161; device sends traps on UDP 162
SNMP versions: v1 and v2c: plaintext community string (v2c adds bulk). v3: authentication, integrity, encryption
Flow data: NetFlow, sFlow, IPFIX: who talked to whom, ports, volume. No payload. Finds top talkers
Packet capture: Protocol analyzer (Wireshark) fed by a SPAN port or an inline tap. Every byte
Syslog severity: 0 Emergency, 1 Alert, 2 Critical, 3 Error, 4 Warning, 5 Notice, 6 Informational, 7 Debug
SIEM: Correlates logs from many sources, alerts on patterns, retains for compliance
Baseline: Normal utilization, latency, errors over time. Anomaly alerts fire on deviation
Solutions: Discovery (ad hoc or scheduled), traffic analysis, performance, availability (uptime versus SLA), configuration monitoring
RPO: Recovery point objective: how much data you can lose, measured backward in time
RTO: Recovery time objective: how fast service must be restored
MTTR: Mean time to repair: average fix time
MTBF: Mean time between failures: average life before failing
Cold site: Space, power, cooling only. Days or weeks. Cheapest
Warm site: Equipment and connectivity in place; restore data. Hours to a day
Hot site: Running mirror with current data. Minutes. Most expensive
Active-active: All nodes serve; capacity drops on failure
Active-passive: Standby takes over on failure (FHRPs)
Tabletop: Walk through the plan on paper. Validation test: actually fail over or restore

Troubleshooting 57

CRC errors and late collisions on one link: Duplex mismatch
Works at 80 m, fails or flaps at 120 m: Attenuation (copper limit 100 m)
Fiber link dead, strands crossed at one end: TX/RX polarity reversal
Runts (under 64 bytes): Collisions or bad NIC
Giants (over MTU): MTU or jumbo frame mismatch
Discards or drops rising: Congestion
Port error-disabled: Port security, BPDU guard, or flapping violation; fix cause then clear
Port administratively down: Someone typed shutdown
Camera or AP powers on then reboots, or never powers: PoE budget exceeded or wrong PoE standard
No link with SR optic on single-mode fiber: Transceiver or fiber mismatch
Interference in a factory over UTP: EMI; use STP or fiber
Broadcast storm, CPU 100 percent, MACs flapping right after a new cable: Spanning tree loop
Odd traffic paths, access switch is root: Root bridge in the wrong place; lower core priority
Host gets an address from the wrong scope after a desk move: Access port in the wrong VLAN
Untagged traffic lands in the wrong VLAN on a trunk: Native VLAN mismatch
Local devices reachable, nothing remote: Wrong or missing default gateway
Some hosts on the same subnet unreachable: Incorrect subnet mask
Intermittent connectivity, address conflict warning: Duplicate IP (static inside a scope without exclusion)
New clients get 169.254.x.x, old ones work: DHCP scope exhaustion or unreachable server
Ping by IP works, by name fails: DNS
One application or port fails, others work: ACL blocking it
Traffic goes out, replies never come back: Missing return route or asymmetric routing through a stateful firewall
Full signal bars, poor throughput: Interference or co-channel overlap; use 1, 6, 11 or move to 5 GHz
Choppy voice, delay varies: Jitter
Everything slow through one link at 100 percent: Bottleneck or congestion
Clients cling to a distant AP: Too little cell overlap or transmit power too high
ping: Reachability, round-trip time, loss. Loopback, self, gateway, remote in that order
traceroute / tracert: Every hop and its latency; where the path breaks. mtr and pathping repeat over time
ipconfig /all, /release, /renew, /flushdns: Windows address, mask, gateway, DNS, lease, MAC; refresh lease; clear resolver cache
ifconfig, ip addr: Linux and macOS addressing
arp -a: IP-to-MAC cache; duplicates and poisoning
nslookup, dig: Query DNS directly, pick a server, ask for a record type
netstat: Open connections and listening ports; netstat -r shows the routing table
nmap: Open ports and services; live hosts on a subnet (authorized use only)
tcpdump, Wireshark: Command-line capture; graphical protocol analyzer
LLDP / CDP: What device and port is on the other end of a cable
show mac-address-table: Which MAC is on which port and VLAN
show arp: The device's ARP cache
show interface: Status, speed, duplex, errors, CRCs, drops
show ip route: Routing table and how each route was learned
show vlan: VLANs and port assignments
show running-config: Current configuration
show power: PoE budget and per-port power
Toner and probe: Find the far end of a cable in a bundle or patch panel
Cable tester: Continuity, pinout, opens, shorts, split pairs, length
Cable certifier: Proves a run meets its category with a report
Punch-down tool, crimper: Terminate on jacks and panels; attach RJ45 plugs
Loopback plug: Tests a port's own transmit and receive
Visual fault locator: Red light shows fiber breaks and bends
OTDR: Locates fiber breaks and losses by distance
Optical power meter: Received light level
Fiber cleaning kit: Dirty connectors are the most common fiber fault
Network tap: Passive inline copy of traffic when there is no SPAN port
Wi-Fi analyzer: APs, channels, signal, dead spots
Spectrum analyzer: All radio energy including non-Wi-Fi interference
Multimeter: Voltage and continuity
PoE injector: Adds power where the switch cannot

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434: 316 Acronyms, 9 The exam itself, 7 IPv4 addressing and subnetting, 10 Switching, 8 Routing, NAT, and gateway redundancy, 9 DHCP, DNS, and time, 18 Network operations, 57 Troubleshooting. They come from the course's cheat sheet and glossary, so what you drill is what the lessons teach.

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