| Access Control List (ACL) | List kept by Cisco routers to control access to or from the router for a number of services |
| Broadcast | Data packet that will be sent to all nodes on a network. Broadcasts are identified by a broadcast address. |
| Broadcast domain | The set of all devices that will receive broadcast frames originating from any device within the set. Broadcast domains are typically bounded by routers because routers do not forward broadcast frames. |
| Broadcast storm | Undesirable network event in which many broadcasts are sent simultaneously across all network segments. |
| Collision domain | In Ethernet, the network area within which frames that have collided are propagated. Repeaters and hubs propagate collisions; LAN switches, bridges and routers do not. |
| Dynamic VLAN | Dynamic VLANs are ports on a switch that can automatically determine their VLAN assignments. |
| Firewall | Router or access server, or several routers or access servers, designated as a buffer between any connected public networks and a private network. |
| Flat network | |
| Frame | Logical grouping of information sent as a data link layer unit over a transmission medium. Often refers to the header and trailer, used for synchronization and error control, that surround the user data contained in the unit. |
| Hub | Hardware or software device that contains multiple independent but connected modules of network and internetwork equipment. |
| MAC (Media Access Control) address | Standardized data link layer address that is required for every port or device that connects to a LAN. Other devices in the network use these addresses to locate specific ports in the network and to create and update routing tables and data structures. |
| Microsegmentation | Division of a network into smaller segments, usually with the intention of increasing aggregate bandwidth to network devices. |
| Multicast | Single packets copied by the network and sent to a specific subset of network addresses. |
| Port | Interface on an internetworking device (such as a router). |
| Port-centric VLAN | In port-centric VLANs, all the nodes connected to ports in the same VLAN are assigned to the same VLAN ID. |