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Networking

This page explains how CoreDNS and the Nginx-Ingress controller work within RKE2.

Refer to the Installation Network Options page for details on Canal configuration options, or how to set up your own CNI.

For information on which ports need to be opened for RKE2, refer to the Installation Requirements.

CoreDNS​

CoreDNS is deployed by default when starting the server. To disable, run each server with disable: rke2-coredns option in your configuration file.

If you don't install CoreDNS, you will need to install a cluster DNS provider yourself.

CoreDNS is deployed with the autoscaler by default. To disable it or change its config, use the HelmChartConfig resource.

NodeLocal DNSCache​

NodeLocal DNSCache improves the performance by running a dns caching agent on each node. To activate this feature, apply the following HelmChartConfig:

---
apiVersion: helm.cattle.io/v1
kind: HelmChartConfig
metadata:
  name: rke2-coredns
  namespace: kube-system
spec:
  valuesContent: |-
    nodelocal:
      enabled: true

The helm controller will redeploy coredns with the new config. Please be aware that nodelocal modifies the iptables of the node to intercept DNS traffic. Therefore, activating and then deactivating this feature without redeploying, will cause the DNS service to stop working.

Note that NodeLocal DNSCache must be deployed in ipvs mode if kube-proxy is using that mode. To deploy it in this mode, apply the following HelmChartConfig:

---
apiVersion: helm.cattle.io/v1
kind: HelmChartConfig
metadata:
  name: rke2-coredns
  namespace: kube-system
spec:
  valuesContent: |-
    nodelocal:
      enabled: true
      ipvs: true

Nginx Ingress Controller​

nginx-ingress is an Ingress controller powered by NGINX that uses a ConfigMap to store the NGINX configuration.

nginx-ingress is deployed by default when starting the server. Ports 80 and 443 will be bound by the ingress controller in its default configuration, making these unusable for HostPort or NodePort services in the cluster.

Configuration options can be specified by creating a HelmChartConfig manifest to customize the rke2-ingress-nginx HelmChart values. For example, a HelmChartConfig at /var/lib/rancher/rke2/server/manifests/rke2-ingress-nginx-config.yaml with the following contents sets use-forwarded-headers to "true" in the ConfigMap storing the NGINX config:

# /var/lib/rancher/rke2/server/manifests/rke2-ingress-nginx-config.yaml
---
apiVersion: helm.cattle.io/v1
kind: HelmChartConfig
metadata:
  name: rke2-ingress-nginx
  namespace: kube-system
spec:
  valuesContent: |-
    controller:
      config:
        use-forwarded-headers: "true"

For more information, refer to the official nginx-ingress Helm Configuration Parameters.

To disable the NGINX ingress controller, start each server with the disable: rke2-ingress-nginx option in your configuration file.

Nodes Without a Hostname​

Some cloud providers, such as Linode, will create machines with "localhost" as the hostname and others may not have a hostname set at all. This can cause problems with domain name resolution. You can run RKE2 with the node-name parameter and this will pass the node name to resolve this issue.