Cisco Certified Support Technician (CCST) Networking: key terms

Flashcards for this exam Cisco Certified Support Technician (CCST) Networking guide Class dates

• 10 Gigabit Ethernet (10GbE)Ethernet at 10 Gbps over copper, twinax or fiber, defined in 802.3ae (fiber) and 802.3an (copper).Foundational
• 1000BASE-TGigabit Ethernet over all four pairs of Cat 5e or better twisted-pair copper, up to 100 meters.Foundational
• 2.4 GHz BandThe 2.400-2.4835 GHz ISM band used by 802.11b/g/n/ax, with only three non-overlapping 20 MHz channels in North America.Foundational
• 5 GHz BandWi-Fi spectrum from about 5.150 to 5.895 GHz divided into U-NII sub-bands, offering many non-overlapping channels.Foundational
• A RecordA DNS record that maps a host name to an IPv4 address.Foundational
• AAAA RecordA DNS record that maps a host name to an IPv6 address.Foundational
• Access LayerThe edge layer of a hierarchical network where end devices connect.Intermediate
• Access PortA switch port that carries traffic for a single data VLAN (plus optionally a voice VLAN) without tagging.Foundational
• Address Resolution Protocol (ARP)The protocol (RFC 826) that resolves a known IPv4 address to the corresponding MAC address on the local network.Foundational
• Administrative DistanceA Cisco value (0-255) ranking the trustworthiness of route sources; the lowest AD wins when protocols offer the same prefix.Foundational
• AntennaA device that converts electrical RF signals into radiated electromagnetic waves and back again.Foundational
• AnycastOne-to-nearest communication in which the same address is assigned to multiple nodes and routing delivers traffic to the closest one.Intermediate
• Application Layer (L7)OSI Layer 7 (and top layer of TCP/IP), which provides network services directly to user applications.Foundational
• ARP CacheThe table a host or router keeps of recently resolved IPv4-to-MAC mappings.Foundational
• ARP CommandA command that displays and modifies the ARP cache on Windows, Linux and macOS.Foundational
• AttenuationThe loss of signal strength as it travels through a medium, measured in decibels.Foundational
• Authoritative Name ServerA DNS server that holds the official records for a zone and answers queries for it with authority.Intermediate
• Automatic Medium-Dependent Interface Crossover (Auto-MDIX)A port feature that detects the cable type and swaps transmit and receive pairs automatically, so either straight-through or crossover cable works.Foundational
• Automatic Private IP Addressing (APIPA)A Windows feature that self-assigns an address from 169.254.0.0/16 when a DHCP server cannot be reached.Foundational
• AutonegotiationAn Ethernet mechanism through which connected devices exchange capabilities and select the highest common speed and duplex.Foundational
• Autonomous Access PointA standalone AP that contains all configuration, management, and control functions locally.Foundational
• BandwidthThe maximum data rate a link or path can carry, expressed in bits per second.Foundational
• Binary-to-Decimal ConversionTranslating between base-2 and base-10 values, an essential skill for IP subnetting.Foundational
• Bits per Second (bps)The unit for data rate on networks, scaled as Kbps, Mbps, Gbps and Tbps using powers of 1000.Foundational
• Block SizeThe increment between consecutive subnet addresses in the interesting octet, equal to 256 minus the mask value in that octet.Foundational
• BridgeA Layer 2 device that connects network segments and forwards frames based on MAC addresses, separating collision domains.Foundational
• BroadcastOne-to-all communication in which a single frame or packet is delivered to every host on the local segment.Foundational
• Broadcast AddressThe last address in an IPv4 subnet, with all host bits set to 1, used to send a packet to all hosts on that subnet.Foundational
• Broadcast DomainThe set of devices that receive each other's Layer 2 broadcasts; bounded by routers or by VLANs.Foundational
• Broadcast MAC AddressThe all-ones MAC address ff:ff:ff:ff:ff:ff, which sends a frame to every device in the broadcast domain.Foundational
• Cable TesterA tool that verifies continuity and correct pinouts on copper cables, detecting opens, shorts and miswires.Foundational
• Canonical Name Record (CNAME)A DNS record that makes one name an alias of another canonical name.Foundational
• Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA)The 802.11 medium access method in which stations sense the medium and back off randomly before transmitting.Foundational
• Carrier Sense Multiple Access with Collision Detection (CSMA/CD)The media access method used by half-duplex Ethernet: listen before sending, detect collisions, and retry after a random backoff.Foundational
• Category 5e Cable (Cat 5e)Enhanced Category 5 UTP rated to 100 MHz, supporting 1000BASE-T and 2.5GBASE-T up to 100 meters.Foundational
• Category 6 Cable (Cat 6)UTP or STP rated to 250 MHz, supporting 1 Gbps to 100 m and 10GBASE-T up to about 55 m.Foundational
• Category 6A Cable (Cat 6a)Augmented Category 6 cable rated to 500 MHz, supporting 10GBASE-T to the full 100 meters.Foundational
• Cisco Discovery Protocol (CDP)Cisco-proprietary Layer 2 protocol that advertises device identity, platform, addresses, VLAN and capabilities to directly connected neighbors.Foundational
• Class A AddressAn IPv4 address with first octet 1-126 (leading bit 0) and a default mask of 255.0.0.0 (/8).Foundational
• Class B AddressAn IPv4 address with first octet 128-191 (leading bits 10) and a default mask of 255.255.0.0 (/16).Foundational
• Class C AddressAn IPv4 address with first octet 192-223 (leading bits 110) and a default mask of 255.255.255.0 (/24).Foundational
• Class D AddressAn IPv4 address in the 224.0.0.0-239.255.255.255 range (224.0.0.0/4), reserved for multicast groups.Foundational
• Classful AddressingThe original IPv4 scheme that divided the address space into fixed classes A through E based on the leading bits.Foundational
• Classless Inter-Domain Routing (CIDR)The addressing scheme (RFC 4632) that replaced classful addressing by allowing any prefix length and route aggregation.Foundational
• Collapsed CoreA two-tier design in which the core and distribution layers are combined in the same devices.Intermediate
• Collision DomainA network segment where frames can collide with one another; every switch port is its own collision domain.Foundational
• Community StringA shared password-like string used for access control in SNMPv1 and SNMPv2c, sent in clear text.Intermediate
• Connected RouteA route automatically installed for the subnet of an interface that is up/up and has an IP address.Foundational
• Connection-Oriented CommunicationCommunication in which a session is established before data transfer and delivery is tracked with acknowledgments.Foundational
• Connectionless CommunicationCommunication in which each message is sent independently with no session setup, acknowledgments or delivery guarantee.Foundational
• Console PortA serial management port on network devices that provides direct command-line access without network connectivity.Foundational
• Core LayerThe backbone layer of a hierarchical network that provides fast, redundant transport between distribution blocks.Intermediate
• CRC ErrorAn interface error counted when a received frame's FCS does not match the computed CRC, indicating corruption.Foundational
• Crossover CableA twisted-pair cable with T568A on one end and T568B on the other, swapping transmit and receive pairs to connect like devices.Foundational
• Cyclic Redundancy Check (CRC)An error-detecting code based on polynomial division, used in Ethernet's FCS and in storage systems.Foundational
• Data Link Layer (L2)OSI Layer 2, which delivers frames between nodes on the same local network using physical (MAC) addresses.Foundational
• DecapsulationThe reverse of encapsulation, in which each layer on the receiver removes and processes its header before passing data up.Foundational
• Decibel-Milliwatt (dBm)Absolute power level in decibels relative to 1 milliwatt (0 dBm = 1 mW).Foundational
• Default GatewayThe router address a host sends traffic to when the destination is on a different subnet.Foundational
• Default RouteThe route 0.0.0.0/0 (or ::/0 in IPv6) that matches any destination not covered by a more specific route.Intermediate
• Demilitarized Zone (DMZ)A network segment between an organization's internal network and the Internet that hosts public-facing services.Foundational
• DHCP Exclusion RangeAddresses within a scope that the DHCP server will not assign, reserved for statically configured devices.Foundational
• DHCP LeaseThe period during which a client may use an address assigned by DHCP.Foundational
• DHCP OptionsAdditional configuration parameters a DHCP server sends to clients, identified by number.Intermediate
• DHCP Relay AgentA router or Layer 3 switch function that forwards DHCP broadcasts from clients to a DHCP server on another subnet as unicast.Intermediate
• DHCP ReservationA DHCP configuration that always assigns the same IP address to a specific client, identified by its MAC address or client ID.Foundational
• DHCP ScopeThe range of IP addresses and associated settings a DHCP server can assign on a particular subnet.Foundational
• DHCPv6The IPv6 version of DHCP, which can assign addresses (stateful) or just options such as DNS servers (stateless).Intermediate
• Distribution LayerThe aggregation layer of a hierarchical network that connects access switches and enforces policy, routing and summarization.Intermediate
• DNS CacheTemporary storage of DNS answers on clients and resolvers for the duration of each record's TTL.Foundational
• Domain Name System (DNS)The hierarchical, distributed system that translates domain names into IP addresses and other records, using UDP and TCP port 53.Foundational
• Domain Name System Security Extensions (DNSSEC)DNS extensions that digitally sign records so resolvers can verify their authenticity and integrity.Intermediate
• DORA ProcessThe four-message DHCP exchange: Discover, Offer, Request, Acknowledge.Foundational
• Dotted-Decimal NotationThe format for writing IPv4 addresses as four decimal numbers (0-255) separated by periods.Foundational
• Dual StackRunning IPv4 and IPv6 simultaneously on the same devices and network.Foundational
• Duplex MismatchA misconfiguration where one end of a link runs full duplex and the other half duplex, causing poor performance.Foundational
• Dynamic Host Configuration Protocol (DHCP)A protocol that automatically assigns IP addresses and other configuration to hosts, using UDP ports 67 (server) and 68 (client).Foundational
• Dynamic IP AddressAn IP address automatically assigned to a device, usually by DHCP, for a limited lease period.Foundational
• East-West TrafficTraffic that moves laterally between servers, workloads or devices within a data center or network.Intermediate
• Electromagnetic Interference (EMI)Unwanted electrical noise from external sources, such as motors, fluorescent lights and power lines, that disrupts signals on copper cabling.Foundational
• EncapsulationThe process of each layer wrapping data from the layer above with its own header (and sometimes trailer) as it moves down the stack.Foundational
• EthernetThe dominant wired LAN technology, standardized as IEEE 802.3, defining framing, MAC addressing and physical media from 10 Mbps to 800 Gbps.Foundational
• Ethernet FrameThe Layer 2 unit Ethernet uses, containing destination MAC, source MAC, EtherType or length, payload and FCS.Foundational
• Ethernet Naming ConventionThe IEEE format rate-BASE-medium (for example 1000BASE-T) that describes an Ethernet physical layer.Foundational
• Fiber Optic CableCable that transmits data as pulses of light through glass or plastic fibers, offering high bandwidth, long distance and immunity to EMI.Foundational
• File Transfer Protocol (FTP)A protocol for transferring files that uses TCP port 21 for control and port 20 (active mode) or a negotiated port (passive mode) for data.Foundational
• FirewallA device or software that permits or denies traffic between networks or hosts according to a security policy.Foundational
• FrameThe Layer 2 PDU, consisting of a header with MAC addresses, a payload, and usually a trailer for error checking.Foundational
• Frame Check Sequence (FCS)The 4-byte Ethernet trailer containing a CRC-32 value used to detect frame corruption.Foundational
• FrequencyThe number of times a wave completes a cycle per second, measured in hertz (Hz).Foundational
• Full MeshA topology in which every node has a direct link to every other node.Intermediate
• Full-DuplexCommunication in which a device sends and receives at the same time over separate paths, eliminating collisions.Foundational
• Fully Qualified Domain Name (FQDN)A complete domain name that specifies a host's exact location in the DNS hierarchy, including all labels up to the root.Foundational
• Gigabit Ethernet (GbE)Ethernet at 1000 Mbps, defined in 802.3z (fiber) and 802.3ab (copper).Foundational
• Global Unicast Address (GUA)A globally routable IPv6 address, currently allocated from 2000::/3.Foundational
• Half-DuplexCommunication in which a device can either send or receive at any moment, but not both at once.Foundational
• Host PortionThe trailing bits of an IP address that identify a specific interface within a subnet.Foundational
• Hosts FileA local text file that maps host names to IP addresses and is checked before DNS on most systems.Foundational
• HubA legacy Layer 1 device that repeats incoming signals out every other port, creating a single shared collision domain.Foundational
• Hub-and-Spoke TopologyA WAN topology in which branch sites (spokes) connect to a central site (hub), and traffic between spokes passes through the hub.Foundational
• Hypertext Transfer Protocol (HTTP)The Application-layer request-response protocol for the web, using TCP port 80 by default.Foundational
• Hypertext Transfer Protocol Secure (HTTPS)HTTP carried inside TLS encryption, using TCP port 443 by default (and UDP 443 for HTTP/3).Foundational
• ICMP Echo ReplyICMP type 0 message returned in response to an echo request, confirming reachability and providing round-trip time.Foundational
• ICMP Echo RequestICMP type 8 message sent by ping to test whether a destination is reachable.Foundational
• IEEE 802.11The IEEE family of standards defining wireless LAN PHY and MAC layers, commonly known as Wi-Fi.Foundational
• IEEE 802.11ac2013 amendment (Wi-Fi 5) for 5 GHz only, adding 80/160 MHz channels, 256-QAM, up to 8 streams, and downlink MU-MIMO.Foundational
• IEEE 802.11n2009 amendment (Wi-Fi 4) adding MIMO, 40 MHz channels, and frame aggregation in 2.4 and 5 GHz, up to 600 Mbps.Foundational
• IEEE 802.1QThe IEEE standard for VLAN tagging that inserts a 4-byte tag with a 12-bit VLAN ID into Ethernet frames.Foundational
• IEEE 802.3The IEEE working group and family of standards that define wired Ethernet physical layers and MAC.Foundational
• Institute of Electrical and Electronics Engineers (IEEE)A professional organization whose standards association publishes the 802 family of LAN and MAN standards.Foundational
• Inter-VLAN RoutingRouting packets between VLANs using a router or Layer 3 switch.Foundational
• Interface ErrorsCounters on network interfaces that track problems such as CRC errors, runts, giants, collisions, drops and discards.Foundational
• Internet Control Message Protocol (ICMP)The Layer 3 protocol (IP protocol 1) used for error reporting and diagnostics, such as ping and traceroute.Foundational
• Internet LayerThe TCP/IP model layer that handles logical addressing and routing, equivalent to OSI Layer 3.Foundational
• Internet Message Access Protocol (IMAP)An email retrieval protocol that keeps messages on the server and synchronizes them across clients, using TCP 143 (or 993 with TLS).Foundational
• Internet Protocol (IP)The connectionless Layer 3 protocol that addresses and routes packets across interconnected networks.Foundational
• Internet Protocol version 4 (IPv4)The fourth version of IP, using 32-bit addresses written in dotted-decimal notation, defined in RFC 791.Foundational
• Internet Protocol version 6 (IPv6)The successor to IPv4, using 128-bit addresses written in hexadecimal, defined in RFC 8200.Foundational
• IP AddressA logical Layer 3 address that identifies a network interface and its network for routing purposes.Foundational
• IP Address ConflictA condition in which two devices on the same network use the same IP address, causing intermittent connectivity for both.Foundational
• IP Configuration Command (ipconfig)The Windows command that displays and manages IP configuration.Foundational
• IPv6 Address CompressionRules for shortening IPv6 addresses: omit leading zeros in each hextet and replace one longest run of all-zero hextets with ::.Foundational
• IPv6 Address NotationIPv6 addresses are written as eight groups of four hexadecimal digits separated by colons, with a /prefix length.Foundational
• IPv6 Link-Local Address (LLA)An IPv6 address in fe80::/10, automatically configured on every IPv6 interface and valid only on the local link.Foundational
• IPv6 Multicast AddressIPv6 addresses in ff00::/8 that identify groups of interfaces, replacing the role of IPv4 broadcast.Intermediate
• JitterThe variation in packet delay over time, which disrupts real-time traffic such as voice and video.Foundational
• LatencyThe time it takes for data to travel from source to destination, usually measured in milliseconds.Foundational
• Lightweight Access Point (LAP)An AP that handles real-time radio functions while a controller manages configuration and control.Foundational
• Lightweight Directory Access Protocol (LDAP)A protocol for querying and modifying directory services such as Active Directory, using TCP/UDP port 389.Foundational
• Link LayerThe lowest layer of the TCP/IP model (also called Network Access or Network Interface) covering OSI Layers 1 and 2.Foundational
• Link Layer Discovery Protocol (LLDP)IEEE 802.1AB vendor-neutral Layer 2 neighbor discovery protocol using TLVs.Foundational
• Link-Local AddressAn address valid only on the local network segment and never forwarded by routers.Intermediate
• Load BalancerA device or service that distributes client requests across multiple servers to improve performance and availability.Foundational
• Local Area Network (LAN)A network covering a limited area such as a home, office or building, usually owned and managed by one organization.Foundational
• Logical TopologyThe way data flows through a network and how devices communicate, independent of physical cabling.Foundational
• Longest Prefix Match (LPM)The forwarding rule that the route with the most specific (longest) matching prefix is used, regardless of AD or metric.Foundational
• Loopback AddressAn address that refers to the local host itself; 127.0.0.0/8 in IPv4 (usually 127.0.0.1) and ::1 in IPv6.Foundational
• Lucent Connector (LC)A small form-factor fiber connector with a 1.25 mm ferrule and push-pull latch, usually used as a duplex pair.Foundational
• MAC AddressA 48-bit Layer 2 address that identifies a network interface on a local network, written as 12 hexadecimal digits.Foundational
• MAC Address TableThe switch table mapping learned source MAC addresses to ports and VLANs, used for frame forwarding (CAM table).Foundational
• Mail Exchanger Record (MX)A DNS record that identifies the mail servers that accept email for a domain, with preference values.Foundational
• Management Information Base (MIB)A hierarchical database definition describing the objects an SNMP agent exposes, such as interface counters and CPU usage.Intermediate
• Maximum Transmission Unit (MTU)The largest Layer 3 packet, in bytes, that a link can carry without fragmentation; 1500 bytes on standard Ethernet.Foundational
• Media ConverterA Layer 1 device that converts signals between different media types, such as copper twisted pair to fiber.Foundational
• Mesh TopologyA topology in which devices have multiple interconnections, providing redundant paths.Foundational
• MetricA protocol-specific value expressing the cost of a path; within one routing protocol the lowest metric route is preferred.Foundational
• MulticastOne-to-many communication delivered only to hosts that have joined a particular group.Foundational
• Multilayer SwitchA switch that can also perform Layer 3 routing (and sometimes higher-layer functions) in hardware.Foundational
• Multimode Fiber (MMF)Fiber with a larger core (50 or 62.5 microns) that carries multiple light paths, used for shorter distances inside buildings and data centers.Foundational
• Name Server Lookup (nslookup)A command-line tool on Windows, Linux and macOS for querying DNS servers.Foundational
• Neighbor Discovery Protocol (NDP)The ICMPv6-based protocol (RFC 4861) that performs address resolution, router discovery, prefix discovery and duplicate address detection in IPv6.Intermediate
• NetFlowA Cisco-originated technology that exports metadata about traffic flows, such as addresses, ports and byte counts, to a collector.Intermediate
• Network AddressThe first address in a subnet, with all host bits set to 0, which identifies the subnet itself.Foundational
• Network Address Translation (NAT)A function that rewrites IP addresses (and often ports) in packet headers as traffic passes through a router or firewall.Foundational
• Network BaselineA record of normal network performance and behavior used to identify anomalies.Foundational
• Network Interface Card (NIC)The hardware that connects a device to a network, providing a physical connection and a MAC address.Foundational
• Network Layer (L3)OSI Layer 3, which provides logical addressing and routing of packets between different networks.Foundational
• Network PortionThe leading bits of an IP address, identified by the subnet mask, that specify which network or subnet the address belongs to.Foundational
• Network Statistics Command (netstat)A command that shows active connections, listening ports, routing tables and interface statistics.Foundational
• Network Time Protocol (NTP)A protocol that synchronizes clocks across network devices and hosts, using UDP port 123.Foundational
• Network TopologyThe arrangement of nodes and links in a network, described physically (cabling) or logically (data flow).Foundational
• Network Troubleshooting MethodologyThe structured seven-step process: identify the problem, establish a theory, test it, plan, implement, verify functionality and document.Foundational
• Non-Overlapping ChannelsChannels whose spectrum does not overlap, such as 1, 6, and 11 in the 2.4 GHz US band.Foundational
• North-South TrafficTraffic that enters or leaves a data center or network, moving between internal systems and external clients.Intermediate
• NTP StratumThe distance of an NTP server from an authoritative reference clock, from stratum 0 (the clock) to 15; stratum 16 means unsynchronized.Intermediate
• Number of Subnets FormulaThe calculation 2^s, where s is the number of borrowed subnet bits, giving how many subnets are created.Foundational
• OctetA group of 8 bits; an IPv4 address contains four octets.Foundational
• Omnidirectional AntennaAn antenna that radiates equally in all horizontal directions in a doughnut-shaped pattern.Foundational
• Open Systems Interconnection Model (OSI model)A seven-layer ISO reference model that describes how data moves from an application on one host to an application on another.Foundational
• Out-of-Band Management (OOB)Managing network devices through a dedicated path separate from production data traffic.Intermediate
• PacketThe Layer 3 PDU, consisting of an IP header plus a transport-layer payload.Foundational
• Packet Internet Groper (ping)A command that tests IP reachability and round-trip time by sending ICMP Echo Requests and waiting for Echo Replies.Foundational
• Packet LossThe percentage of packets that fail to reach their destination.Foundational
• Packet SwitchingA method in which data is divided into packets that are forwarded independently and share network links with other traffic.Foundational
• Partial MeshA topology in which some nodes have multiple connections but not every node connects to every other.Intermediate
• Physical Layer (L1)OSI Layer 1, which transmits raw bits as electrical, optical or radio signals over a medium.Foundational
• Physical TopologyThe actual layout of cables, devices and connections in a network.Foundational
• PoE Plus (PoE+)IEEE 802.3at, which delivers up to 30 W per port at the switch (25.5 W at the device) over two pairs.Foundational
• Point-to-Point TopologyA direct link between exactly two endpoints.Foundational
• Pointer Record (PTR)A DNS record that maps an IP address to a host name, used for reverse lookups.Foundational
• Port Address Translation (PAT)NAT that maps many inside addresses to one (or a few) public addresses by tracking unique source port numbers; also called NAT overload.Foundational
• Port Mirroring (SPAN)A switch feature that copies traffic from one or more ports or VLANs to a monitoring port for analysis.Intermediate
• Port NumberA 16-bit number (0-65535) that identifies a specific application or service on a host at Layer 4.Foundational
• Post Office Protocol 3 (POP3)An email retrieval protocol that downloads messages from a server to a client, using TCP 110 (or 995 with TLS).Foundational
• Power over Ethernet (PoE)Delivering DC power and data together over twisted-pair Ethernet cabling, standardized in IEEE 802.3af, 802.3at and 802.3bt.Foundational
• Prefix LengthThe number of leading network bits in an address, written after a slash, as in /24 or /64.Foundational
• Private IP AddressIPv4 addresses reserved by RFC 1918 for internal use: 10.0.0.0/8, 172.16.0.0/12 and 192.168.0.0/16.Foundational
• Protocol AnalyzerA tool that captures and decodes network traffic so it can be examined protocol by protocol.Foundational
• Protocol Data Unit (PDU)The name for the unit of data at a given layer, such as bits, frame, packet, segment or data.Foundational
• Proxy ServerA server that acts as an intermediary for requests between clients and other servers.Foundational
• Public IP AddressA globally unique, Internet-routable IP address assigned by an ISP or registry.Foundational
• Radio Frequency (RF)Electromagnetic energy in the roughly 3 kHz to 300 GHz range used to carry data wirelessly.Foundational
• Real-time Transport Protocol (RTP)A protocol that carries real-time audio and video over UDP, with sequence numbers and timestamps for playback timing.Intermediate
• Recursive DNS ResolverA DNS server that accepts queries from clients and performs the full lookup process on their behalf, caching results.Intermediate
• Registered Jack 45 (RJ45)The common name for the eight-position, eight-contact (8P8C) modular connector used on Ethernet twisted-pair cables.Foundational
• Remote Desktop Protocol (RDP)Microsoft's protocol for remote graphical access to Windows systems, using TCP and UDP port 3389.Foundational
• RepeaterA Layer 1 device that regenerates and retransmits a signal to extend the distance a network can cover.Foundational
• Rogue DHCP ServerAn unauthorized DHCP server that hands out incorrect addressing, causing outages or enabling on-path attacks.Intermediate
• Rollover CableA cable with pins reversed end to end (1 to 8, 2 to 7 and so on), used to connect a computer serial port to a network device console port.Foundational
• Round-Trip Time (RTT)The time for a packet to travel to a destination and for the response to return.Foundational
• RouterA Layer 3 device that forwards packets between different IP networks based on destination IP address and its routing table.Foundational
• Router Advertisement (RA)An ICMPv6 type 134 message routers send periodically and in response to RS, advertising prefixes, the default gateway and configuration flags.Intermediate
• Routing TableThe router's table of best known paths to destination prefixes, built from connected, static and dynamic routing sources.Foundational
• Running ConfigurationThe active configuration held in RAM on Cisco IOS devices, distinct from the startup configuration stored in NVRAM.Foundational
• Secure Shell (SSH)An encrypted protocol for remote command-line access, tunneling and file transfer, using TCP port 22.Foundational
• SegmentThe Layer 4 PDU produced by TCP, consisting of a TCP header and a chunk of application data.Foundational
• Server Message Block (SMB)The Windows file and printer sharing protocol, running directly over TCP port 445.Foundational
• Service Set Identifier (SSID)The human-readable name of a wireless network, up to 32 octets.Foundational
• Session Initiation Protocol (SIP)A signaling protocol that sets up, modifies and tears down VoIP and video sessions, using port 5060 (unencrypted) and 5061 (TLS).Foundational
• Show Interfaces CommandThe Cisco IOS command that displays an interface's status, speed, duplex, counters and errors.Foundational
• Simple Mail Transfer Protocol (SMTP)The protocol for sending email and relaying it between mail servers, using TCP port 25 (server-to-server) and 587 (client submission).Foundational
• Simple Network Management Protocol (SNMP)A traditional UDP-based protocol for monitoring and managing network devices using MIBs, polling (ports 161) and traps (port 162).Foundational
• Single-Mode Fiber (SMF)Fiber with a very small core (about 9 microns) that carries a single light path, supporting distances of tens to hundreds of kilometers.Foundational
• Small Form-Factor Pluggable (SFP)A hot-swappable transceiver module, typically 1 Gbps, that plugs into a switch or router port to provide fiber or copper connectivity.Foundational
• Small Form-Factor Pluggable Plus (SFP+)An enhanced SFP module supporting 10 Gbps, physically compatible with SFP ports.Foundational
• SNMP TrapAn unsolicited message an SNMP agent sends to a manager on UDP 162 when a significant event occurs.Intermediate
• SNMPv3The secure version of SNMP, providing user-based authentication, message integrity and encryption.Intermediate
• Spine-and-Leaf ArchitectureA two-tier data center design in which every leaf switch connects to every spine switch, giving predictable, low-latency paths.Intermediate
• SSH File Transfer Protocol (SFTP)A secure file transfer protocol that runs as a subsystem of SSH over TCP port 22.Foundational
• Star TopologyA topology in which every node connects to a central device such as a switch.Foundational
• Stateful FirewallA firewall that tracks the state of connections and automatically allows return traffic for sessions initiated from trusted networks.Foundational
• Stateless Address Autoconfiguration (SLAAC)An IPv6 method in which hosts build their own addresses from a router-advertised /64 prefix plus a self-generated interface ID.Foundational
• Static IP AddressAn IP address manually configured on a device that does not change unless an administrator changes it.Foundational
• Static NATA one-to-one, permanent mapping between a private (inside local) address and a public (inside global) address.Foundational
• Static RouteA manually configured route to a destination prefix through a next-hop address or exit interface.Foundational
• Straight-Through CableA twisted-pair cable with the same pinout (both T568A or both T568B) on each end, used to connect unlike devices.Foundational
• SubnetA logical subdivision of an IP network defined by a network address and prefix length.Foundational
• Subnet MaskA 32-bit value with contiguous 1 bits marking the network portion of an IPv4 address and 0 bits marking the host portion.Foundational
• SubnettingDividing a larger IP network into smaller subnets by borrowing host bits for the network portion.Foundational
• Subscriber ConnectorA square fiber connector with a 2.5 mm ferrule and push-pull latching, common in older enterprise and FTTH installations.Foundational
• SwitchA Layer 2 device that forwards frames to specific ports based on destination MAC addresses it has learned.Foundational
• SyslogA standard for sending event log messages to a central collector, traditionally over UDP port 514.Foundational
• Syslog Severity LevelsThe eight syslog message levels from 0 (Emergency) to 7 (Debugging).Intermediate
• T568AA TIA wiring standard for RJ45 terminations with pin order green-white, green, orange-white, blue, blue-white, orange, brown-white, brown.Foundational
• T568BA TIA wiring standard for RJ45 terminations with pin order orange-white, orange, green-white, blue, blue-white, green, brown-white, brown.Foundational
• TCP/IP ModelThe four-layer model of the Internet protocol suite: Link (Network Access), Internet, Transport and Application.Foundational
• TelnetA legacy protocol for remote command-line access over TCP port 23 that sends everything, including passwords, in clear text.Foundational
• Three-Tier ArchitectureA hierarchical campus design with core, distribution and access layers, each with distinct roles.Intermediate
• Three-Way HandshakeThe SYN, SYN-ACK, ACK exchange TCP uses to establish a connection and synchronize sequence numbers.Foundational
• ThroughputThe actual rate of successful data delivery over a link or path, usually lower than the rated bandwidth.Foundational
• TIA/EIA-568 StandardThe TIA standard family for commercial building telecommunications cabling, defining cable categories, distances, pinouts and installation practices.Foundational
• Time to Live (TTL)An 8-bit IPv4 header field decremented by each router; when it reaches zero the packet is discarded to prevent endless looping.Foundational
• TracerouteA tool that discovers the routers along the path to a destination by sending probes with increasing TTL values.Foundational
• TransceiverA device that both transmits and receives signals, typically a pluggable module converting electrical signals to optical or copper media.Foundational
• Transmission Control Protocol (TCP)A connection-oriented Layer 4 protocol that provides reliable, ordered, error-checked delivery of a byte stream.Foundational
• Transport Layer (L4)OSI Layer 4, which provides host-to-host delivery, segmentation, port addressing and optionally reliability.Foundational
• Transport Layer Security (TLS)The cryptographic protocol that secures application traffic with encryption, integrity and certificate-based authentication; successor to SSL.Foundational
• Trivial File Transfer Protocol (TFTP)A simple, unauthenticated file transfer protocol using UDP port 69.Foundational
• Trunk PortA switch port that carries multiple VLANs over one link, identifying them with 802.1Q tags.Foundational
• Twisted PairCopper cabling in which pairs of insulated wires are twisted together to cancel electromagnetic interference and crosstalk.Foundational
• UnicastOne-to-one communication from a single sender to a single receiver.Foundational
• Unshielded Twisted Pair (UTP)Twisted-pair cable without metallic shielding, relying only on twisting to reject interference; the most common LAN cable.Foundational
• Usable Hosts FormulaThe calculation 2^h - 2, where h is the number of host bits, giving the assignable IPv4 addresses in a subnet.Foundational
• User Datagram Protocol (UDP)A connectionless Layer 4 protocol that sends datagrams with minimal overhead and no delivery, ordering or retransmission guarantees.Foundational
• Virtual Local Area Network (VLAN)A logical Layer 2 broadcast domain created on switches, independent of physical location.Foundational
• Voice over IP (VoIP)Technology that carries voice calls as packets over IP networks instead of traditional circuit-switched lines.Foundational
• Well-Known PortsPorts 0-1023, assigned by IANA to common system services such as HTTP, SSH and DNS.Foundational
• Wide Area Network (WAN)A network spanning large geographic areas, connecting LANs across cities, countries or continents, usually over provider services.Foundational
• Wireless LAN Controller (WLC)A device or virtual appliance that centrally manages lightweight APs, RF, security, and client policy.Foundational
• WiresharkA free, open-source graphical protocol analyzer that captures and decodes network packets.Foundational