Huawei HCIA-Datacom key terms

A seven-layer framework that describes how data moves between networked applications, from the physical cabling up to the user-facing application. Each layer performs a distinct job and relies on the services of the layer directly below it.

The process of wrapping data with protocol-specific headers (and sometimes trailers) as it passes down the protocol stack, so each layer can deliver the payload to the correct peer on the far end.

The exchange of SYN, SYN-ACK and ACK segments that opens a TCP connection. It lets both hosts agree on starting sequence numbers and confirm that each side can both send and receive.

A 48-bit hardware identifier burned into or assigned to a network interface, written as six hexadecimal byte pairs. Switches use it to forward frames within a local network segment.

Address Resolution Protocol. A host broadcasts a request asking which MAC address owns a given IPv4 address, and the owner replies, letting the sender build a frame for the local link.

A 32-bit pattern, often written as a slash number such as /24, that marks which bits of an IPv4 address identify the network and which identify the host. Devices use it to decide if a destination is local or remote.

The IP address of a router interface on the local subnet. A host sends traffic to this address whenever the destination is not on its own subnet, because the router knows how to reach other networks.

A route an administrator configures by hand, specifying a destination network, a mask and a next hop or outbound interface. It does not adapt automatically when the topology changes unless it is tracked or withdrawn.

The rule routers apply when several routes match a destination: the entry with the most specific mask, meaning the greatest number of network bits, is chosen and installed in the forwarding table.

Open Shortest Path First. A link-state interior gateway protocol in which routers flood link information, build an identical topology database, and run the shortest path first algorithm to compute loop-free routes.

A logical Layer 2 broadcast domain created inside switches, letting one physical infrastructure carry several isolated networks. Frames stay within their VLAN unless a router or Layer 3 switch forwards them.

A switch port that belongs to a single VLAN and connects to an end device such as a PC or server. Frames leaving it are normally sent untagged.

A switch port that carries traffic for multiple VLANs between switches or toward a router, marking each frame with its VLAN identifier so the receiver can keep the traffic separated.

A four-byte field inserted into an Ethernet frame header that carries a 12-bit VLAN identifier plus priority bits, allowing many VLANs to share one physical link.

Spanning Tree Protocol. A Layer 2 mechanism that elects a root bridge and blocks redundant paths, producing a loop-free tree so broadcast frames cannot circulate forever in a meshed switched network.

Bridge Protocol Data Unit. The control message switches exchange when running spanning tree; it carries bridge priority, MAC address and path cost information used to elect the root and select forwarding ports.

Bundling several physical links between two devices into one logical link, which increases bandwidth, provides redundancy, and avoids the blocked ports that spanning tree would otherwise create.

Access Control List. An ordered set of permit and deny rules that match packet fields such as source address, destination address, protocol and port. Packets are checked against the rules in sequence.

Authentication, Authorization and Accounting. A framework in which users are first proven to be who they claim, then granted defined privileges, and finally have their activity recorded for audit.

Network Address Translation. A router rewrites the source or destination IP address in packet headers as traffic crosses between networks, commonly letting many private hosts reach the internet through public addresses.

Network Address Port Translation, often called address overload or PAT. Many internal hosts share a single public address, and the router distinguishes their sessions by translating transport port numbers as well.

Dynamic Host Configuration Protocol. A server automatically supplies clients with an IP address, mask, default gateway, DNS servers and other options, typically through Discover, Offer, Request and Acknowledge messages.

Point-to-Point Protocol. A Layer 2 protocol for direct links between two devices that supports link negotiation, optional authentication, and multiplexing of multiple network protocols over the same circuit.

High-level Data Link Control. A simple, vendor-oriented synchronous framing protocol for point-to-point serial links; it flags frame boundaries and provides error detection but no authentication or protocol multiplexing.

PPP over Ethernet. It carries PPP sessions inside Ethernet frames so subscribers can be authenticated and given an address per session, which is common on broadband access networks.

Challenge Handshake Authentication Protocol. The server sends a random challenge, the peer returns a hash of that challenge plus a shared secret, and the exchange may be repeated later to guard against replay.

Simple Network Management Protocol. A manager polls agents in network devices or receives traps from them, reading and writing values in a structured management information base to monitor and control the devices.

Network Time Protocol. It synchronises device clocks to reference time sources over the network, keeping timestamps consistent so that logs, certificates and scheduled tasks across devices line up correctly.

Secure Shell. An encrypted remote login and command protocol that replaces plaintext Telnet for device management, protecting credentials and configuration traffic from eavesdropping on the network.

A standard for generating, formatting and shipping event messages from network devices to a collector. Messages carry a severity level and facility, making centralised troubleshooting and retention possible.

Trivial File Transfer Protocol. A minimal UDP-based file transfer service with no authentication, frequently used to back up or restore device configurations and to load software images on a local network.

A publicly routable IPv6 address from the 2000::/3 range, normally built from a routing prefix supplied by an operator plus a 64-bit interface identifier, and configured on interfaces that must reach the internet.

An address in fe80::/10 that every IPv6 interface forms automatically and uses only on its local link, for neighbour discovery, routing protocol adjacencies and next-hop reachability without any global prefix.

The IPv6 protocol suite that uses ICMPv6 to resolve link-layer addresses, detect neighbours, advertise routers, and perform duplicate address detection, replacing the role ARP plays in IPv4.

Stateless Address Autoconfiguration. A host builds its own IPv6 address from a router-advertised prefix and an interface identifier, needing no DHCP server to obtain an address, though other options may still come from DHCPv6.

Software-Defined Networking. An architecture that separates the control plane, where forwarding decisions are computed, from the forwarding plane, and centralises control in software so the network can be programmed as a whole.

Virtual Extensible LAN. A tunnelling technology that encapsulates Layer 2 frames inside UDP packets, extending a Layer 2 segment across a routed Layer 3 network and supporting far more segments than 802.1Q VLAN IDs allow.

VXLAN Tunnel Endpoint. The device that encapsulates frames from a local segment into VXLAN packets and decapsulates traffic arriving from the tunnel, identified by an IP address on the underlay network.

An interface built on HTTP where resources are addressed by URLs and manipulated with standard methods such as GET, POST, PUT and DELETE, commonly returning JSON so controllers and scripts can automate configuration.

A network management protocol that runs over SSH, exchanges XML-encoded configuration data, and supports candidate configurations, validation and transaction-style commits, making automated device changes reliable and reversible.