Plain-English definitions of the networking terms for CCNA study. Simplified for learning; Cisco’s material is authoritative.
| Term | Definition |
|---|---|
| Subnet | A logical division of an IP network. |
| Subnet mask | Defines which part of an IP is network vs host. |
| CIDR | Slash notation for a subnet mask (e.g., /24). |
| Default gateway | The router a device uses to reach other networks. |
| VLAN | A logical segment of a switched network. |
| Trunk | A link carrying multiple VLANs (802.1Q tagging). |
| STP | Spanning Tree Protocol — prevents switching loops. |
| EtherChannel | Bundled links acting as one for bandwidth/redundancy. |
| Routing table | The list a router uses to choose paths. |
| Static route | A manually configured route. |
| OSPF | A link-state dynamic routing protocol. |
| Administrative distance | Trustworthiness ranking of a route source. |
| NAT | Network Address Translation, private to public. |
| PAT | Port Address Translation — many private IPs to one public. |
| ACL | Access Control List — filters traffic by rules. |
| DHCP | Automatically assigns IP addresses. |
| DNS | Resolves names to IP addresses. |
| Switch vs router | Forwards within a LAN vs between networks. |
| Port security | Restricts which devices can use a switch port. |
| REST API | A web interface used in network automation. |