CCST Networking key terms

A seven-layer reference framework describing how data moves from an application on one host to an application on another, covering physical signaling through user-facing services.

A four-layer practical framework (link, internet, transport, application) that maps to how real networks and the Internet actually operate, and to which OSI layers are often compared.

The process of wrapping data with headers (and sometimes trailers) at each layer as it moves down the stack, so each layer can add the information its peer layer needs.

The named data unit at a given layer, such as a frame at the link layer, a packet at the network layer, and a segment at the transport layer.

A 48-bit hardware identifier burned into a network interface, written as six hexadecimal octets, used for delivery on a single local network segment.

The first 24 bits of a MAC address, assigned to a manufacturer, letting you identify the vendor of a network interface from its address alone.

A 32-bit logical address written as four decimal octets, split into a network portion and a host portion by its subnet mask or prefix length.

A 32-bit value of contiguous ones followed by zeros that marks which bits of an IPv4 address identify the network and which identify the host.

A shorthand that writes an address followed by a slash and the count of network bits, such as /24, replacing the older dotted-decimal mask form.

The address formed when all host bits are set to zero; it names the subnet itself and cannot be assigned to a device interface.

The address with all host bits set to one; a packet sent to it is delivered to every host on that subnet and it cannot be assigned to an interface.

An IPv4 range reserved for internal use (10/8, 172.16/12, 192.168/16) that is not routable on the public Internet without translation.

A self-assigned address in 169.254.0.0/16 that a host gives itself when no DHCP server answers, which usually signals a DHCP or link problem.

A 128-bit logical address written as eight hexadecimal groups, designed to remove address scarcity and to support stateless autoconfiguration.

An address valid only on one segment, such as IPv4 169.254.0.0/16 or IPv6 fe80::/10, used before or instead of routable addressing.

A method where an IPv6 host builds its own address from a router-advertised prefix plus an interface identifier, without a DHCP server.

A protocol that automatically supplies hosts with an IP address, mask, default gateway, and DNS servers from a pool managed by a server.

The router address a host sends traffic to when the destination is not on its own subnet; a wrong value breaks off-subnet connectivity.

A hierarchical system that resolves human-readable names to IP addresses, letting users reach services without memorizing numeric addresses.

The dominant wired LAN technology, defining frame format, addressing, and media signaling for speeds from 10 Mbps to hundreds of gigabits per second.

The link-layer data unit, which carries source and destination MAC addresses, a payload, and a trailer with a frame check sequence.

The network-layer data unit, carrying source and destination IP addresses plus a payload, routed hop by hop toward its destination network.

The largest payload size a link will carry in one frame; exceeding it forces fragmentation or packet drops, which is a common cause of odd application failures.

Copper cabling with four twisted wire pairs terminated in RJ45 plugs, the standard for office Ethernet runs at distances up to 100 meters.

Cabling that carries data as pulses of light through glass or plastic strands, supporting long distances and high bandwidth free of electrical interference.

A small hot-swappable transceiver module that plugs into a switch or router port to provide an optical or copper uplink of a chosen type.

A device that learns MAC addresses per port and forwards frames only to the port where the destination is known, dividing a network into collision domains.

A switch's internal mapping of learned MAC addresses to ports, built by reading source addresses of incoming frames and used to decide where to forward.

A switch behavior that sends a frame out all ports except the one it arrived on, used when the destination MAC is unknown, broadcast, or multicast.

A logical grouping of switch ports that behaves as a separate broadcast domain, letting one physical switch host multiple isolated networks.

A switch port that carries traffic for multiple VLANs by tagging frames with a VLAN identifier, typically used for links between switches.

A device that forwards packets between different IP networks by consulting a routing table and rewriting link-layer headers at each hop.

A list of destination networks with next-hop and metric information that a router uses to choose where to send each packet.

A translation technique that rewrites private source addresses to a public address as traffic leaves a network, letting many hosts share one public IP.

A device that bridges wireless clients onto a wired network, advertising a service set identifier and enforcing the chosen security settings.

The name a wireless network broadcasts so clients can find and join it; hiding it does not provide real security.

A frequency slice within a Wi-Fi band; overlapping channels on nearby access points cause interference and reduced throughput.

A utility that sends ICMP echo requests to test whether a host is reachable and to measure round-trip time and packet loss.

A tool that reveals each router hop along a path by sending packets with increasing time-to-live values and collecting the returned errors.

A command-line tool that displays a host's address, mask, gateway, and DNS settings, and can release or renew DHCP leases.

A handheld device that checks continuity, pinout, and pair wiring on copper links, identifying opens, shorts, and crossed pairs.