- OSI Model
- A seven-layer conceptual framework (Physical, Data Link, Network, Transport, Session, Presentation, Application) used to describe how network communication functions and to standardize troubleshooting and protocol design.
- VLAN (Virtual Local Area Network)
- A logical grouping of switch ports that creates a separate broadcast domain, allowing devices to be segmented by function or department regardless of physical location.
- Trunk Port
- A switch port configured to carry tagged traffic for multiple VLANs simultaneously, typically using the 802.1Q tagging standard.
- Spanning Tree Protocol (STP)
- A Layer 2 protocol that prevents bridging loops in networks with redundant switch links by selectively blocking ports while maintaining backup paths for failover.
- EtherChannel
- A link aggregation technology that bundles multiple physical Ethernet links between two switches into a single logical link for increased bandwidth and redundancy.
- OSPF (Open Shortest Path First)
- A link-state interior gateway routing protocol that uses a cost metric based on bandwidth to calculate the shortest path to each destination network.
- EIGRP (Enhanced Interior Gateway Routing Protocol)
- A Cisco-proprietary advanced distance-vector routing protocol that uses a composite metric and the DUAL algorithm to select loop-free paths.
- Administrative Distance
- A value used by a router to rank the trustworthiness of a routing information source; when multiple sources offer a route to the same destination, the router prefers the one with the lowest administrative distance.
- ACL (Access Control List)
- An ordered list of permit or deny statements applied to a router or switch interface to filter traffic based on criteria such as source/destination address or port.
- NAT (Network Address Translation)
- A technique that translates private IP addresses used inside a network into public IP addresses for communication with external networks, and vice versa.
- DHCP (Dynamic Host Configuration Protocol)
- A protocol that automatically assigns IP addresses and other network configuration parameters (such as default gateway and DNS servers) to hosts on a network.
- DNS (Domain Name System)
- A distributed naming system that resolves human-readable domain names to IP addresses, enabling users to reach network resources without memorizing numeric addresses.
- ARP (Address Resolution Protocol)
- A protocol used to map a known IPv4 address to its corresponding MAC address on a local network segment.
- Default Gateway
- The router interface address a host uses to send traffic destined for networks outside its own local subnet.
- CIDR (Classless Inter-Domain Routing)
- A method of allocating IP addresses and routing using variable-length subnet masking, expressed in slash notation (e.g., /24) to denote the number of network bits.
- Subnetting
- The process of dividing a larger IP network into smaller, more manageable subnetworks by borrowing bits from the host portion of an address for the network portion.
- Broadcast Domain
- The set of all devices that receive a broadcast frame sent by any one device within that domain; broadcast domains are bounded by routers.
- Collision Domain
- A network segment where data frames sent by devices can collide with one another; each switch port on a full-duplex link forms its own collision domain.
- HSRP (Hot Standby Router Protocol)
- A Cisco-proprietary first-hop redundancy protocol that allows multiple routers to present a single virtual default gateway IP address, providing failover if the active router goes down.
- 802.1Q
- The IEEE standard for VLAN tagging that inserts a tag into an Ethernet frame to identify which VLAN the frame belongs to as it crosses a trunk link.
- QoS (Quality of Service)
- A set of techniques for classifying, marking, and prioritizing network traffic to ensure critical or latency-sensitive applications receive appropriate bandwidth and low delay.
- SDN (Software-Defined Networking)
- A network architecture that separates the control plane from the data plane and centralizes it in a controller, enabling programmatic, centralized management of network devices.
- NETCONF/RESTCONF
- Network management protocols that use structured, machine-readable data (XML for NETCONF, JSON/XML for RESTCONF) to programmatically configure and retrieve state from network devices, commonly used in automation.