CNI Plugins vs Flannel
CNI Plugins
github.comFlannel
github.comSide by side
| Figure | CNI Plugins | Flannel |
|---|---|---|
| Price from | Free | Free |
| Free plan | Yes | Yes |
| Free trial | — | — |
| Open source | — | — |
| Windows | Yes | Yes |
| Linux | Yes | Yes |
| Self-hosted | — | Yes |
| Plans published | 1 | 1 |
| Spec score · Container Networking Software | 7.8 (#8) | 7.8 (#10) |
| Purpose | CNI Plugins is a collection of reference and example network plugins maintained by the containernetworking team. | Flannel provides a layer 3 network fabric for containers designed for Kubernetes. |
| Security reporting | The project asks that security issues be reported privately to the email addresses listed in its OWNERS file. | The security policy directs vulnerability reports to GitHub private vulnerability reporting and says maintainers acknowledge reports within seven days. |
| Support | The project directs questions to the cni-dev mailing group or the #cni channel on CNCF Slack. | The project points users to the #k3s channel in Rancher Users Slack, the #flannel-users channel in Calico Users Slack, and GitHub issues for bugs. |
Plans
In their own words
CNI Plugins
CNI Plugins is a collection of reference and example network plugins for configuring connectivity in Linux and Windows containers. CNI supplies a specification and libraries, plus a command-line tool for executing plugins and a Go library for application integration. Interface options include bridge, ipvlan, loopback, macvlan, point-to-point, VLAN, host-device, and dummy; Windows-specific plugins include win-bridge and win-overlay. IP address management choices cover DHCP, host-local allocation tracking, and static IPv4 or IPv6 allocation. Meta plugins handle interface tuning, port mapping, bandwidth limits, source-based routing, and firewall rules, and a sample plugin illustrates custom plugin development. CNI focuses on connecting containers and removing allocated resources when a container is deleted. The project is distributed under Apache License 2.0 and is a Cloud Native Computing Foundation project. It is free, with a plan listed at free. Linux and Windows are supported; the latest release page lists Linux archives for amd64, arm, and arm64.
Flannel
Flannel is a free network fabric for containers designed for Kubernetes. A small flanneld agent on each host allocates a subnet lease from a configured address space, then forwards packets between hosts using a selected backend. Documented choices include VXLAN, host-gw, WireGuard and UDP, with VXLAN recommended. WireGuard encapsulates and encrypts packets using the in-kernel WireGuard implementation. Network configuration and subnet allocations can be stored in the Kubernetes API or directly in etcd. The project documents Kubernetes and Docker deployments, with Linux and Windows build instructions. Flannel does not enforce network policies itself, though its Helm chart can deploy a Kubernetes SIGs network policy controller alongside it. It runs as a privileged daemonset with access to the host network, so the security policy advises least privilege and keeping it updated. Security fixes are maintained for the latest release only, and the backend documentation says not to change a selected backend at runtime.