flannel
Container networking software
DevOps software
Containerization software
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What is flannel
Flannel is an open-source container network interface (CNI) plugin that provides a simple layer-3 network fabric for Kubernetes clusters. It assigns each node a subnet and routes pod traffic between nodes using backends such as VXLAN, host-gw, or an external routing option. Platform teams use it to establish basic pod-to-pod connectivity in self-managed clusters, often where advanced network policy or service-mesh features are not required. It is commonly deployed as a DaemonSet and integrates with Kubernetes via standard CNI configuration.
Simple Kubernetes pod networking
Flannel focuses on establishing basic pod-to-pod connectivity across nodes with minimal configuration. It is widely used as a default or starter CNI in self-managed Kubernetes environments. The operational model is straightforward (node subnets plus an overlay or routing backend), which reduces setup complexity for small to mid-sized clusters.
Multiple networking backends
Flannel supports several backends (for example VXLAN overlay and host-gw routing), allowing teams to choose between encapsulation and direct routing based on their infrastructure. This flexibility helps it run across different environments, including on-premises and cloud VMs. Backend selection can be aligned with performance, network constraints, and operational preferences.
Open-source and broadly integrated
Flannel is open source and integrates with Kubernetes through the CNI standard, which makes it compatible with common cluster bootstrapping tools and distributions. It has a large installed base and extensive community documentation and examples. This reduces vendor lock-in and supports common operational patterns such as GitOps-based configuration management.
Limited network policy capabilities
Flannel primarily provides connectivity and does not natively deliver comprehensive Kubernetes NetworkPolicy enforcement on its own. Organizations that require fine-grained, identity-aware, or L7-aware policy typically need additional components or a different CNI. This can increase architectural complexity for security-focused deployments.
Fewer advanced observability features
Compared with more feature-rich container networking stacks, Flannel offers limited built-in visibility into flows, policy decisions, and service-level networking behavior. Teams often rely on external tooling for deep troubleshooting and traffic analytics. This can lengthen incident investigation time in larger or more regulated environments.
Overlay performance and MTU tuning
When using encapsulation backends such as VXLAN, Flannel can introduce overhead and may require careful MTU configuration to avoid fragmentation issues. Performance characteristics depend heavily on the chosen backend and underlying network. High-throughput or latency-sensitive workloads may need benchmarking and tuning or an alternative approach.
Plan & Pricing
Pricing model: Open-source / Free (Apache-2.0) Free tier/trial: Permanently free (no trial required) Example costs: None — flannel is distributed under the Apache-2.0 license and has no paid SKUs or subscription plans. Notes: Project source, releases, and documentation are available on the official GitHub repository (flannel-io/flannel).
Seller details
Flannel (open-source project; originally created by CoreOS, now maintained in the Kubernetes ecosystem)
Open Source
https://github.com/flannel-io/flannel
