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Cloud Infrastructure > Containers > Containers Resources > What is CoreOS Flannel? Definition

What is CoreOS Flannel? Definition

Flannel is a networking technology used to connect Linux Containers. It is distributed and maintained by CoreOS, the producer of the stripped-down CoreOS Linux operating system for containers, as well as the rkt container system that competes with Docker.

Although tailored for use with the CoreOS operating system, Flannel is also compatible with Docker. Flannel emerged as an alternative method for container networking, originating from an open-source concept originally called Rudder, which in 2014 was renamed to Flannel.  It was written in the Go programming language.

CoreOS Flannel vs. Container Networking Alternatives

There are many different ways to network Linux containers, all with different architectural approaches. Docker’s native networking scheme creates a virtual layer 3 Ethernet bridge, which automatically forwards packets between containers through a subnet routing scheme.   Google Kubernetes assigns unique IP addresses to collective pods for which containers are members. When it first emerged, this was a more sophisticated form of software-defined networking employed by Kubernetes to direct traffic between containers, and thus to enable microservices.

Flannel is a basic overlay network that works by assigning a range of subnet addresses (usually IPv4 with a /24 subnet mask).  Each address corresponds to a container, so that all containers in a system may reside on different hosts.  By using packet encapsulation, Flannel enables the entire span of hosts to be addressed, by assigning a separate subnet to each host.  Flannel uses the open source etcd key/value store to record the mappings between the addresses assigned to containers by their native hosts, and their addresses in the overlay network.

As a result, complex, multi-host systems such as Hortonworks Hadoop can be distributed across multiple Docker container hosts, using Flannel as the underlying fabric [see Figure 1].

Flannel proponents say that the system resolves a deficiency in Docker’s original (native) container address mapping system, in which each container’s address was effectively an exclusive port assigned to the same host.  Thus container systems could not span hosts, limiting the system’s effectiveness on cloud platforms.  Docker Inc. has since resolved this deficiency, with the acquisition in March 2015 of SDN provider SocketPlane, and the immediate integration of its container networking technology into Docker networking.

How CoreOS Flannel Works with Kubernetes

Kubernetes was first tested at Google, and then within the open-source community, prior to the existence of Flannel.  Its container mapping scheme was designed for Google Compute Engine (the public part of the same platform where Kubernetes was first engineered), but not other public cloud platforms.  Flannel was advanced as a solution to that problem, enabling container systems to span multiple hosts on Amazon EC2 Container Service.  Since that time, however, Kubernetes has evolved substantially, enabling orchestration for container systems spanning a tremendous number of hosts across multiple public and private cloud platforms.

Aside from Kubernetes, Flannel continues to be advanced as a simple, yet effective, way to achieve container networking with scalability beyond a single host.  Yet others see benefits in using both together, with Flannel serving as the fabric layer that provides subnets to Kubernetes for use with pods.  Both Kubernetes and Flannel use /24 subnet masks in their addressing schemes, and CoreOS distributes Kubernetes with its rkt container system.

Additional CoreOS Flannel Resources

Download:  Inside the Linux Container Ecosystem Report

View Online:  Inside the Linux Container Ecosystem Report

How Does Container Networking Work? Defined

Containers vs. VMs

What is the Docker Container and Open Source Project

Docker Acquires Networking Startup SocketPlane

What are Containers?

How Does a Docker Container Work? Explanation

Introducing flannel: An etcd backed overlay network for containers

Docker overlay network using Flannel

How to Install and Configure Kubernetes on Top of a CoreOS Cluster

Configuring Flannel for Container Networking

 

Resources

  • SD-WAN Resources
    • What is Software-Defined WAN (or SD-WAN or SDWAN)?
    • The Essentials of SD-WAN Architecture: Advantages and Options
    • SD-WAN as a Service Using Orchestration
    • What is Hybrid WAN and Why Does it Matter?
    • What’s the Difference Between Hybrid WAN and SD-WAN
    • What is SDN-WAN and Why Does it Matter?
    • What is SD-WAN as a Service?
    • What is iWAN and Why Does It Matter?
    • What is the Difference Between SD-WAN and iWAN?
    • SD-WAN vs. MPLS: The Pros and Cons of Both Technologies
    • Riverbed SD-WAN Offers Different Options
    • What Is CloudGenix’s SD-WAN Approach?
    • What Is AT&T’s SD-WAN Approach?
    • Versa’s SD-WAN Combines Networking and Security
    • Nuage’s SD-WAN Uses a Single Network Policy Framework
    • What is Citrix’s SD-WAN Product?
    • What Is Cisco’s SD-WAN Approach?
    • What Is Juniper’s SD-WAN Approach?
    • Silver Peak’s SD-WAN Solution Targets Enterprises
    • What is Verizon’s SD-WAN Approach?
    • What Is VeloCloud’s SD-WAN Approach?
    • What Is Viptela’s SD-WAN Approach?
    • 2017 SD-WAN and Virtual Edge Report – Download
  • MEC Resources
    • What Is Multi-Access Edge Computing (MEC)?
  • Containers Resources
    • Inside the Linux Container Ecosystem Report – Download
    • What are Containers?
    • How Does Container Networking Work?
    • Containers vs VMs: Which is better in the Data Center?
    • What is Docker Container? Part 1: The Docker Open Source Project
    • What is Docker Container? Part 2: How Docker Containers Work
    • What Is Docker Security & How Do You Use It?
    • What is the Docker Platform and Container Components?
    • What is CoreOS Flannel?
  • SDN Resources
    • What is Software Defined Networking (SDN)? Definition
    • Software-Defined Networking Tutorial – The Basics
    • Why SDN or NFV Now?
    • What are SDN Northbound APIs (and SDN Rest APIs)?
    • What are SDN Southbound APIs?
    • What is Open SDN?
    • What is the OpenDaylight Project (ODL)?
    • What is OpenFlow?
    • Who is the Open Networking Foundation (ONF)?
    • What are SDN Controllers?
    • SDN, NFV, and Network Virtualization Define The Wave of New IP Infrastructure
    • Understanding the SDN Architecture – SDN Control Plane & SDN Data Plane
    • What’s a Software-defined Data Center?
    • What is SDN-WAN and Why Does it Matter?
    • SDN Webinar Videos, Presentations, and Demos
    • What is SDN Orchestration (SDN Policy Orchestration)?
    • 2015 SDN & NFV Market Size and Forecast Report
    • What is the Brocade SDN Controller (BSC)?
    • What is Cisco APIC? Part 2 of Cisco ACI Definition
    • What is Cisco Application Policy Infrastructure Controller (APIC)? Part 3
    • What is a Cisco XNC (Extensible Network Controller)?
    • What is a Floodlight Controller?
    • What is the Juniper Contrail Controller?
    • What is the NEC OpenFlow ProgrammableFlow Controller?
    • What is an OpenDaylight Controller?
    • What is an OpenFlow Controller?
    • What is Ryu Controller?
    • What is Cyan Blue Planet?
    • What is Nuage Networks VSC?
    • What is the Software Driven Cloud Networking?
    • SDN Controller Comparison Part 1: SDN Controller Vendors (SDN Controller Companies)
  • Network Virtualization Resources
    • What is Network Virtualization?
    • What is Overlay Networking (SDN Overlay)?
    • What is Network Automation With Network Virtualization?
    • What is Virtual Networking?
    • What is Network Service Chaining?
    • What are Network Overlays?
    • What is Networking as a Service or NaaS?
    • What is a VXLAN?
    • What is Network Service Chaining?
    • What Is Network Automation With Network Virtualization?
    • Business Agility Drives Network Virtualization Demand
    • What Is Open Virtual Network (OVN)?
    • How Does Micro-Segmentation Help Security?
    • What is Juniper Networks Network Virtualization?
    • What is NEC Network Virtualization?
    • What is Nuage Network Virtualization?
    • What is Cisco Network Virtualization?
    • How Does Micro-Segmentation Help Security?
  • NFV Resources
    • What is Network Functions Virtualization (NFV)?
    • What is a Virtual Network Function or VNF?
    • What is an NFV POC?
    • Which is Better – SDN or NFV?
    • How Does ETSI NFV Operate?
    • What is ETSI ISG NFV?
    • What is OPNFV or Open Platform for NFV Project?
    • What is NFV MANO?
    • What’s CloudNFV?
    • What’s NFV Software?
    • What’s in an NFV Cloud?
    • What’s a Virtual Router (vRouter)?
    • What is an NFV Strategy?
    • An Overview of NFV Elements
    • What is an NFV Data Center?
    • NFV Webinar Videos, Presentations, and Demos
    • What is an NFV OpenStack?
    • What is an NFV Orchestration?
    • What is an NFV Orchestrator (NFVO)?
    • What is Virtualized Infrastructure Manager (VIM)?
    • What is a VNF Manager (VNFM)?
  • Cloud Resources
    • What is the Cloud?
    • What is Private Cloud? The Benefits and the Providers
    • What is Hybrid Cloud? A Scalable and Customizable Computing Solution
    • What is Software Defined Everything – Part 1: Definition of SDx
    • Software Defined Everything Part 2: Cloud Infrastructure
    • Software Defined Everything Part 3: SDx infrastructure
    • Software Defined Everything Part 4: SDx Infrastructure Buyers
    • Software Defined Everything Part 5: SDx Use Cases
    • Software Defined Everything Part 6: Infrastructure Attributes
    • Software Defined Everything Part 7: Infrastructure Form Factors & Delivery Models
    • Software Defined Everything Part 8: Succeeding in an SDx World
    • What are Cloud Service Providers?
    • Introduction to Cloud Infrastructure
    • What is Software-Defined Storage?
    • What is Software Defined Compute?
    • What is Storage Virtualization?
    • What is KVM?
    • What is Cloud Networking or Cloud Based Networking?
    • What is the Definition of IEEE Intercloud?
  • Security Resources
    • 2017 SDx Infrastructure Security Report – Download
    • SDN Security – Challenges Implementing SDN Network Security in SDN Environments
    • What is Security Virtualization?
    • What is Cloud-Based Security?
    • Data Security Regulations
    • How to Deliver Data Center Security via Network Virtualization
    • The Top Cloud Security Tools for Threat Monitoring & Threat Protection
    • Future of Virtual Security: Micro-Segmentation & Visibility
  • Open Source Resources
    • What is OpenStack Networking?
    • What is OpenStack Neutron?
    • What is Open vSwitch (OVS)?
    • What is Open vSwitch Database or OVSDB?
    • What is KVM?
    • What Is Mirantis OpenStack?
  • White Box Resources
    • What is White Box Switching & White Box Switches (& are they SDN Switches)?
    • What is a Data Center Fabric?
    • What is a Networking Switch Fabric?
    • What Are 40G Switches?
    • What is a Cisco Nexus Switch?
    • What Is Cisco Application Centric Infrastructure (or Cisco ACI or Cisco SDN)? Part 1
    • What are Leaf Switches?
    • What is a Spine Switch?
  • DevOps Resources
    • SDN Automation, Programmability, and Programmable Networks
  • Cisco Resources
    • What is Cisco OpenFlow?
    • What is Cisco OpFlex?
    • What is the Cisco ONE Controller?
    • What is Cisco Application Centric Infrastructure (ACI)? Part 1
    • What is Cisco APIC? Part 2
    • What is the Cisco Application Policy Infrastructure Controller (APIC)? Part 3
    • What is Cisco onePK?
    • What is a Cisco Nexus Switch?
    • What is a Cisco XNC (Extensible Network Controller)?
    • What is Cisco Network Virtualization?
    • What Is Cisco’s SD-WAN Approach?
    • Cisco Data Center Channel
  • VMware Resources
    • What is VMware NSX and VMware SDN?
    • What is VMware Network Virtualization?
  • Arista Networks Resources
    • What are Arista Switches?

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