Short definitions for frequently used networking, operations, security, and troubleshooting terms.
| Term | Definition |
|---|---|
| AAA | Authentication, authorization, and accounting for access control |
| APIPA | IPv4 link-local self-assignment in 169.254.0.0/16 when DHCP configuration does not complete |
| CIDR | Prefix notation such as /24 or /64 that identifies an IP network boundary |
| FHRP | First-hop redundancy protocol; provides a resilient default gateway |
| IDS | Intrusion detection system; observes and alerts on suspicious activity |
| IPS | Intrusion prevention system; detects and can act inline to block traffic |
| Jitter | Variation in packet delay over time |
| MTBF | Mean time between failures |
| MTTR | Mean time to repair or restore service |
| NAC | Network access control; decides whether and how a device joins a network |
| NAT | Network address translation |
| PAT | Port address translation; many hosts share an address through port mapping |
| PKI | Public key infrastructure; certificates, keys, and trust services |
| PoE | Power over Ethernet |
| RPO | Recovery point objective; maximum acceptable data-loss interval |
| RTO | Recovery time objective; maximum acceptable service-outage interval |
| SLAAC | Stateless IPv6 address configuration based on router advertisements |
| SPAN | Cisco term for port mirroring to an analyzer interface |
| SSID | Wireless network name |
| STP | Spanning Tree Protocol; prevents Layer 2 switching loops |
| TDR | Time-domain reflectometer; estimates fault location in a copper cable |
| VPC | Virtual private cloud; a logically isolated cloud network |
| VLAN | Virtual LAN; a logical Layer 2 segment |
| VXLAN | Virtual extensible LAN; an overlay that extends Layer 2 segments over an IP fabric |
See Network Quick Reference for common distinctions and Technical Resources for standards and primary documentation.