This network glossary gathers the essential terms to know for understanding, choosing, and managing a corporate infrastructure — from switches to VLANs, from PoE to SFP. The definitions are intentionally concise and listed in alphabetical order.
Network Terms from A to Z
IP Address — numeric identifier assigned to each device on a network, allowing it to be addressed (e.g., 192.168.1.10). See our subnet calculator.
MAC Address — unique physical identifier embedded in each network card, used by switches to direct traffic.
Link Aggregation (LACP) — grouping multiple physical links into a single logical link to increase bandwidth and redundancy.
Auto-MDI/MDIX — feature that automatically detects the cable type (straight or crossover), making crossover cables unnecessary.
Bandwidth (throughput) — amount of data transferable per second, expressed in Mbps or Gbps.
Broadcast — frame sent to all devices on the same network segment.
CIDR — subnet mask notation as a suffix (e.g., /24), indicating the number of network bits.
Switch — device that connects devices on a local network and directs traffic to the correct recipient. See our network switches.
Layer 2 / Layer 3 — OSI model layers: layer 2 switches based on MAC addresses, layer 3 routes based on IP addresses.
DHCP — service that automatically assigns IP addresses to devices on the network.
DNS — system that translates domain names (example.com) into IP addresses.
Ethernet — standard technology for wired local networks, over copper (RJ45) or fiber.
Fiber Optic — medium transmitting light for very high speeds over long distances. See our guide fiber or copper.
Full Duplex — mode allowing simultaneous sending and receiving.
Gigabit — speed of 1000 Mbps (1 Gbps), the current standard for enterprise networks.
Latency — transmission delay of a packet, expressed in milliseconds.
Subnet Mask — value that separates the network part from the host part of an IP address.
NAT — address translation that allows a private network to communicate via a single public IP address.
Firewall — security device that filters and controls traffic between the network and the Internet. See our firewalls.
PoE / PoE+ — power supply to devices (cameras, Wi-Fi access points, phones) via Ethernet cable. See our PoE budget calculator.
Port Access / Port Trunk — an access port belongs to a single VLAN; a trunk port carries multiple VLANs simultaneously.
QoS (Quality of Service) — mechanism that prioritizes certain traffic (voice, for example) to ensure smoothness.
QSFP — high-density transceiver for very high speeds (40/100 Gbps). See our SFP/QSFP modules.
Rack U — height unit of a server rack (1U = 44.45 mm).
RJ45 — 8-pin copper Ethernet connector. See our RJ45 wiring reference.
Router — device that connects different networks and routes packets between them. See our enterprise routers.
SFP / SFP+ — removable transceiver inserted into a switch for fiber or copper connection (1G / 10G). See our guide SFP, SFP+ and QSFP.
Subnet — segment of an IP network, defined by a mask, that isolates and organizes addresses.
Spanning Tree (STP) — protocol that prevents loops in a network with redundant links.
Managed Switch — configurable switch (VLAN, QoS, monitoring), as opposed to an unmanaged model. See our guide managed or unmanaged switch.
Uplink — uplink connection linking a switch to the network core or a higher-level device.
VLAN — virtual local network that segments a physical network into multiple isolated logical networks. See our guide VLAN.
To learn more, browse all our network switches, routers, firewalls, and tested and guaranteed used SFP modules, as well as our complete Ethernet switch guide.