Networking terminology

Definitions to common open networking terminology

Data center networking is full of complex terminology and abbreviations. In this networking glossary, you'll find definitions to common data center networking terms, commands and solutions.


Access Control List (ACL)

An ACL applies rules to switch ports or IP addresses available to a host or switch. The rules determine whether or not packets can flow through those ports or IPs.

Address Resolution Protocol (ARP)

A communications protocol used by IPv4 to map an IP address to a physical machine address.

Advanced Package Tool (APT)

Free software that installs and removes software packages from some Linux operating systems, such as Debian

Any Source Multicast (ASM)

A multicast where hosts can transmit to/from groups without any restrictions on the receivers

Application-specific Integrated Circuit (ASIC)

An integrated circuit customized for a specific use


Bare metal switch

A physical network switch without a proprietary operating system. For example, a switch purchased directly from Edgecore and you can install Cumulus Linux or another open OS.

BGP Unnumbered

Unnumbered interfaces don't have unique IP addresses. For BGP, you configure unnumbered interfaces using extended next-hop encoding (ENHE).

Border Gateway Protocol (BGP)

An exterior gateway protocol that exchanges routing and reachability information among autonomous systems

Broadcast, Unknown Unicast, Multicast (BUM)

3 types of network traffic. Unicast involves communication from one single point to another single point. Broadcast is when information is sent from a single point to multiple points. Multicast is communication of information from multiple points to other points.


Capital Expense/Expenditure (CapEx)

The funds that a company spends on physical assets, such as equipment

Cisco Discovery Protocol (CDP)

The proprietary version of LLDP

Clos architecture

Another term for a leaf/spine network

Command Line Interface (CLI)

The interface through which one interacts with a computer program

Continuous Delivery (CI/CD)

The process of making continual improvement rather than a configure-and-forget mentality to IT configuration management

Continuous Integration (CI/CD)

The process of making continual improvement rather than a configure-and-forget mentality to IT configuration management

Cumulus Multichassis Aggregation Group (Cumulus MLAG)

Enables a server or switch with a two-port bond (such as a link aggregation group/LAG, EtherChannel, port group or trunk) to connect those ports to different switches and operate as if they are connected to a single, logical switch. 

Cumulus Virtual Experience (Cumulus VX)

A virtual appliance that runs on many popular hypervisors helping you preview Cumulus Networks technology


Device Driver

A computer program that tells the OS how to communicate with a piece of hardware

Domain Name Service (DNS)

A protocol that translates domain names into IP addresses

Dynamic Host Configuration Protocol (DHCP)

A way to automatically assign IP addresses and settings to a network device


Equal-Cost Multi-Path routing (ECMP)

A load sharing routing strategy where a packet being forwarded to the next hop on the way to a destination can travel over multiple best paths

Ethernet Virtual Private Networks (EVPN)

A standards-based control plane for VXLAN that enables building VXLANs at scale. EVPN allows legacy layer 2 applications to operate over next-generation layer 3 networks.

Explicit Congestion Notification (ECN)

An extension to the Internet Protocol and the Transmission Control Protocol that allows end-to-end notification of network congestion without dropping packets

Extended Support Release (ESR)

One of two branches of Cumulus Networks code. The ESR branch focuses on stability, so only critical-impact security fixes and urgent bug fixes are added to the code.


FRRouting (FRR)

A modern open source routing application that evolved from the original Quagga project


No terms starting with "G"


Hardware Compatibility List (HCL)

A list of all hardware that is compatible with the Cumulus Linux OS

Head End Replication (HER)

Used to generate BUM traffic in hardware to multiple VXLAN destinations (VTEPs)

High-Frequency Trading (HFT)

A form of rapid trading that is based on highly sophisticated programs and algorithms. They are usually short-term investments, characterized by high speed and sensitivity to latency.



Updated Linux interface manager

Internet Group Management Protocol (IGMP)

A communications protocol that enables an Internet computer to report its multicast group membership to adjacent routers


No terms starting with "J"


No terms starting with "K"


Layer 3 (L3)

The layer of the OSI stack concerned with IP addresses; the routing layer.

Lightweight Directory Access Protocol (LDAP)

An open, vendor-neutral, industry standard application protocol for accessing and maintaining distributed directory information services over an Internet protocol network

Lightweight Network Virtualization (LNV)

A technique for deploying VXLANs without a central controller on bare metal switches

A method to control the bundling of several physical ports together to form a single logical channel

Used by network devices to advertise their identity, capabilities and neighbors on an Ethernet network

Local Area Network (LAN)

A computer network that interconnects computers within a limited geographic area


Maximum Transmission Unit (MTU)

The largest size packet or frame that can be communicated in a network transaction

Enables a server or switch with a two-port bond (such as a link aggregation group/LAG, EtherChannel, port group or trunk) to connect those ports to different switches and operate as if they are connected to a single, logical switch. 


Network Access Control (NAC)

A set of protocols to define and implement a policy that describes how to secure access to network nodes by devices when they initially attempt to access the network

Network Command Line Utility (NCLU)

The Cumulus CLI, a rich and simple command line interface for easy network configuration and operation

Network Operating System (NOS)

The operating system that runs on network switches. Cumulus Linux is a NOS.

Network Operations

Network Operations are actions completed within an organization’s network that comprise of tasks such as monitoring, troubleshooting, capturing packets,provisioning network resources, responding to critical issues that arise and more.


Open Compute Project (OCP)

A collaborative community seeking to improve hardware technology and infrastructure design

Open Network Application Platform (ONAP)

A real-time, policy-driven tool for orchestration and automation of physical and virtual network functions

Open Network Install Environment (ONIE)

An Open Compute Project open source initiative contributed by Cumulus Networks that defines an open “install environment” for bare metal network switches. ONIE is a bootloader for NOSes.

Open Shortest Path First (OSPF)

A link-state routing protocol for IPv4 (OSPFv2) and IPv6 (OSPFv3)

Operating Expense/Expenditure (OpEx)

Funds that a company spends on operations

OSPF Unnumbered

Interfaces without unique IP addresses. OSPF unnumbered interfaces reduce the links between routers into pure topological elements, which dramatically simplifies network configuration and reconfiguration.

Out of Band (OOB)

Refers to data that is transferred outside of the data plane network, used for management traffic


Power over Ethernet (PoE)

A network protocol that enables Ethernet cables to carry electric power for devices

Prescriptive Topology Manager (PTM)

A dynamic cabling verification tool developed by Cumulus Networks. With PTM, you can program your data center to verify network connections and resolve issues faster.

Priority Flow Control (PFC)

A link-level flow control mechanism that can be controlled independently for each Class of Service (CoS) with the intention to ensure no data frames are lost when congestion occurs in a bridged network

Protocol Independent Multicast (PIM)

A multicast control plane protocol that advertises multicast sources and receivers over a routed layer 3 network. Has sparse and dense modes of operation.



Original open source routing application in Cumulus Linux, replaced by FRRouting


Rack Management Platform (RMP)

A Cumulus Networks solution that provides an out-of-band management switch preinstalled with a NOS

RDMA over Converged Ethernet (RoCE)

A protocol for writing to compute or storage elements using remote direct memory access (RDMA) over an Ethernet network instead of using host CPUs

Redistribute Neighbor

A mechanism for IP subnets to span racks without forcing the end hosts to run a routing protocol

Remote Authentication Dial-In User Service (RADIUS)

A protocol that provides centralized authentication, authorization and accounting management (AAA) for users connected to a network device or service

Route In and Out of Tunnels (RIOT)

The ability for an ASIC to do VXLAN Routing

Route Reflector (RR)

A network routing component for BGP that acts as an alternative to the full-mesh of IBGP


Simple Network Management Protocol (SNMP)

Simple network management protocol, a troubleshooting tool for monitoring computer networks

Software-defined Data Center (SDDC)

As opposed to traditional data centers, where infrastructure is defined by hardware, SDDCs are comprised of virtualized infrastructure (networking, storage, CPU and security) that is delivered as a service. 

Software-defined Networking (SDN)

A cloud computing strategy that facilitates network management and enables programmatically efficient network configuration in order to improve network performance and monitoring

Source Specific Multicast (SSM)

A secure method of delivering multicast packets, where the receiver only receives packets from the specific source address they requested

Switch Abstraction Interface (SAI)

An open source framework that enables ASICs to be represented in software, specifically in the user space; a Microsoft contribution to the OCP


Terminal Access Controller Access Control System (TACACS)

An authentication protocol used for remote authentication and related services for networked access control through a centralized server

Top of Rack (ToR)

A network architecture where servers within a rack are connected to one or two network switches within the same rack

Total Cost of Ownership (TCO)

The combined cost of CapEx and OpEx


No terms starting with "U"


Virtual Extensible LAN (VXLAN)

A standard overlay protocol that abstracts logical virtual networks from the physical network underneath. You can deploy simple and scalable layer 3 Clos architectures while extending layer 2 segments over that layer 3 network.

Virtual Lan (VLAN)

Separate virtual networks on the same physical network; network packets are tagged so traffic flows to the appropriate VLAN. Thus you can keep network applications separate despite being connected to the same physical network, and without requiring multiple sets of cabling and networking devices to be deployed.

Virtual network

An isolated or abstracted network within a larger network.

Virtual Router Redundancy (VRR)

Enables hosts to communicate with any redundant router without reconfiguration, running dynamic router protocols or running router redundancy protocols. Thus, redundant routers will respond to ARP requests from hosts.

Virtual Routing and Forwarding (VRF)

Run multiple network paths without the need for multiple switches, giving you traffic isolation and network segmentation for multiple devices. It's achieved through the presence of multiple independent routing tables working simultaneously on the same router or switch.

Virtual Tunnel End Point (VTEP)

Physical or virtual switch that is the termination point for one member of a multi-tenant network. A VTEP connects to other VTEPs in other tenants via VXLAN tunnels.

VXLAN Network Identifier (VNI)

The ID used by VXLAN for a VXLAN tunnel

VXLAN routing

Sometimes referred to as inter-VXLAN routing, it provides IP routing between VXLAN VNIs in overlay networks. The routing of traffic is based on the inner header or the overlay tenant IP address.


Web-scale networking

A modern architectural approach that enables networks to scale to the level of cloud giants, such as AWS. Key constructs for this architecture include: open and modular, intelligence in software, scalable and efficient.

White box switch

Same as a bare metal switch: a physical network switch without an operating system. For example, a switch purchased directly from Edge Core without Cumulus Linux.


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No terms starting with "Y"


Zero Touch Provisioning (ZTP)

A switch feature that enables automation of provisioning and configuration