Networking 101
Acronym Reference
Decode networking acronyms — ACL, OSPF, BGP, DHCP, VLAN, NAT and 80+ more
| Acronym | Meaning & Context |
|---|---|
| AAA | Authentication, Authorization, Accounting — security framework for controlling access |
| ACL | Access Control List — permit/deny rules for traffic filtering |
| ARP | Address Resolution Protocol — maps IP addresses to MAC addresses |
| AS | Autonomous System — a network under one organisation's control, identified by an ASN |
| ASN | Autonomous System Number — unique ID for BGP routing between organisations |
| BGP | Border Gateway Protocol — the routing protocol of the internet |
| BPDU | Bridge Protocol Data Unit — messages exchanged by STP to prevent loops |
| CAM | Content Addressable Memory — the MAC address table inside a switch |
| CDP | Cisco Discovery Protocol — Cisco's neighbor discovery protocol |
| CIDR | Classless Inter-Domain Routing — slash notation for subnets (e.g. /24) |
| CLI | Command Line Interface — text-based configuration interface |
| CRC | Cyclic Redundancy Check — error detection for Ethernet frames |
| CSMA/CD | Carrier Sense Multiple Access / Collision Detection — old shared Ethernet access method |
| DAI | Dynamic ARP Inspection — security feature that validates ARP packets on a switch |
| DHCP | Dynamic Host Configuration Protocol — auto-assigns IP addresses to devices |
| DMZ | Demilitarized Zone — isolated network segment for public-facing servers |
| DNS | Domain Name System — translates names to IP addresses |
| DSCP | Differentiated Services Code Point — QoS field in IP header for traffic prioritisation |
| EIGRP | Enhanced Interior Gateway Routing Protocol — Cisco's fast interior routing protocol |
| EVPN | Ethernet VPN — control plane for VXLAN overlays |
| FTP | File Transfer Protocol — transfers files between systems (port 20/21, unencrypted) |
| GRE | Generic Routing Encapsulation — tunneling protocol |
| HSRP | Hot Standby Router Protocol — Cisco's gateway redundancy protocol |
| HTTP | Hypertext Transfer Protocol — web traffic (port 80, unencrypted) |
| HTTPS | HTTP Secure — encrypted web traffic using TLS (port 443) |
| ICMP | Internet Control Message Protocol — used by ping and traceroute |
| IDF | Intermediate Distribution Frame — floor/wing wiring closet |
| IDS | Intrusion Detection System — monitors for suspicious activity, alerts only |
| IGP | Interior Gateway Protocol — routing protocol within an autonomous system (OSPF, EIGRP) |
| IOS | Internetwork Operating System — Cisco's router/switch OS |
| IPS | Intrusion Prevention System — like IDS but can block threats |
| IPsec | IP Security — framework for encrypted VPN tunnels |
| IPv4 | Internet Protocol version 4 — 32-bit addresses (most common) |
| IPv6 | Internet Protocol version 6 — 128-bit addresses |
| ISP | Internet Service Provider |
| LACP | Link Aggregation Control Protocol — IEEE standard for bundling ports (EtherChannel) |
| LAN | Local Area Network — private network within a building |
| LLDP | Link Layer Discovery Protocol — open standard neighbor discovery |
| LSDB | Link State Database — the OSPF topology map stored in each router |
| LSA | Link State Advertisement — the routing update packets in OSPF |
| MAC | Media Access Control — hardware address of a NIC |
| MDF | Main Distribution Frame — central wiring hub |
| MPLS | Multiprotocol Label Switching — WAN technology for routing via labels, not IPs |
| MTU | Maximum Transmission Unit — largest packet a link can carry (standard: 1500 bytes) |
| NAT | Network Address Translation — rewrites IP addresses at the router |
| NIC | Network Interface Card — hardware that connects a device to the network |
| NHRP | Next Hop Resolution Protocol — used in DMVPN for dynamic tunnel building |
| NTP | Network Time Protocol — synchronises clocks across devices (port 123) |
| OSFP | (typo for OSPF) Open Shortest Path First |
| OSPF | Open Shortest Path First — link-state interior routing protocol |
| PAT | Port Address Translation — NAT where many IPs share one public IP via ports |
| PDU | Protocol Data Unit — the name for data at each OSI layer (frame, packet, segment) |
| PoE | Power over Ethernet — power delivery over network cable |
| QoS | Quality of Service — traffic prioritisation policies |
| RADIUS | Remote Authentication Dial-In User Service — AAA protocol for network access |
| RFC | Request for Comments — standards documents that define internet protocols |
| RIP | Routing Information Protocol — simple distance-vector routing protocol (max 15 hops) |
| RIB | Routing Information Base — the routing table |
| RPF | Reverse Path Forwarding — multicast loop prevention mechanism |
| RSTP | Rapid Spanning Tree Protocol — faster version of STP (802.1w) |
| SFP | Small Form-factor Pluggable — hot-swap transceiver module |
| SMTP | Simple Mail Transfer Protocol — sends email (port 25/587) |
| SNMP | Simple Network Management Protocol — monitoring and management (port 161/162) |
| SPF | Shortest Path First — the algorithm OSPF uses to calculate routes (Dijkstra) |
| SSH | Secure Shell — encrypted remote CLI access (port 22) |
| SSID | Service Set Identifier — the Wi-Fi network name |
| STP | Spanning Tree Protocol — prevents Layer 2 loops |
| TACACS+ | Terminal Access Controller Access-Control System Plus — Cisco AAA protocol |
| TCP | Transmission Control Protocol — reliable, connection-oriented transport (Layer 4) |
| TLS | Transport Layer Security — encryption protocol used by HTTPS, SSH, etc. |
| UDP | User Datagram Protocol — fast, connectionless transport (Layer 4) |
| VLAN | Virtual LAN — logical network segmentation on a switch |
| VoIP | Voice over IP — phone calls carried over the data network |
| VPN | Virtual Private Network — encrypted tunnel over untrusted network |
| VRF | Virtual Routing and Forwarding — separate routing tables on one device |
| VRRP | Virtual Router Redundancy Protocol — open standard gateway redundancy |
| VTEP | VXLAN Tunnel Endpoint — device that encapsulates/decapsulates VXLAN traffic |
| VXLAN | Virtual Extensible LAN — overlay protocol that extends VLANs over Layer 3 |
| WAN | Wide Area Network — network spanning large geographic areas |
| WAP | Wireless Access Point — broadcasts Wi-Fi |
| WCCP | Web Cache Communication Protocol — Cisco protocol for redirecting web traffic |
Tip: Use Ctrl+F or the search box above. For full definitions, check the Jargon Decoder tool.