Glossary¶
Quick definitions for terms used throughout this wiki, alphabetical. Each links to the page with full detail.
ACL (Access Control List) — a set of permit/deny rules filtering traffic by IP, protocol, or port. See Access Control Lists.
ARP (Address Resolution Protocol) — resolves an IP address to the MAC address needed for Layer 2 delivery. See MAC Addresses & ARP.
BPDU (Bridge Protocol Data Unit) — the message switches exchange to run Spanning Tree. See Spanning Tree Protocol.
CIDR (Classless Inter-Domain Routing) — the /24-style notation for subnet masks. See IP Subnetting.
DHCP (Dynamic Host Configuration Protocol) — automatically assigns IP addresses and network settings to clients. See DHCP Fundamentals.
DSCP (Differentiated Services Code Point) — a Layer 3 traffic-priority marking used by QoS. See Quality of Service (QoS).
EtherChannel / LAG (Link Aggregation) — bundling multiple physical links into one logical link. See EtherChannel / Link Aggregation.
Gateway — the router/device a host sends traffic to when the destination is outside its own subnet. See Cisco IOS Routing Fundamentals.
LACP (Link Aggregation Control Protocol) — the standard dynamic negotiation protocol for EtherChannel. See EtherChannel / Link Aggregation.
MAC Address — the 48-bit hardware address identifying a network interface at Layer 2. See MAC Addresses & ARP.
NAT (Network Address Translation) — translates private IP addresses to public ones, most commonly via PAT/overload. See NAT & Private IP Ranges.
NVRAM — non-volatile memory storing a switch's startup-config. See File Locations.
OSI Model — the 7-layer conceptual framework for network communication. See The OSI Model.
PAT (Port Address Translation) — sharing one public IP across many internal hosts, distinguished by port number; also called NAT Overload. See NAT & Private IP Ranges.
PoE (Power over Ethernet) — delivering electrical power over an Ethernet cable alongside data. See Power over Ethernet.
QoS (Quality of Service) — prioritizing certain traffic over others during congestion. See Quality of Service (QoS).
RSPAN (Remote SPAN) — mirroring traffic to a monitoring device on a different switch. See Port Mirroring (SPAN).
RFC 1918 — the standard defining the private IP address ranges (10.x, 172.16-31.x, 192.168.x). See NAT & Private IP Ranges.
Running-config — a switch's active configuration in RAM, lost on reboot unless saved. See File Locations.
SNMP (Simple Network Management Protocol) — protocol for polling device status and receiving alerts. See SNMP.
SPAN (Switched Port Analyzer) — port mirroring, copying traffic to a monitoring port. See Port Mirroring (SPAN).
Startup-config — the configuration loaded from NVRAM at boot. See File Locations.
STP (Spanning Tree Protocol) — prevents Layer 2 loops on redundant links. See Spanning Tree Protocol.
SVI (Switched Virtual Interface) — a logical Layer 3 interface assigned to a VLAN, used for inter-VLAN routing. See VLANs & Inter-VLAN Routing.
Syslog — the standard for logging device events, locally or to a remote server. See Syslog.
TCP / UDP — the two Layer 4 transport protocols; TCP is reliable/connection-oriented, UDP is connectionless. See TCP vs UDP & Common Ports.
Trunk Port — a switch port carrying multiple tagged VLANs, typically between switches. See VLANs & Inter-VLAN Routing.
UPS (Uninterruptible Power Supply) — battery backup protecting equipment from power loss. See Power Redundancy.
VLAN (Virtual Local Area Network) — a logical grouping of switch ports isolated at Layer 2. See VLANs & Inter-VLAN Routing.
VTP (VLAN Trunking Protocol) — propagates a VLAN database automatically across switches. See VTP.