Enable Consul DNS proxy for Kubernetes

This page describes the process to deploy a Consul DNS proxy in a Kubernetes Pod so that Services can resolve Consul DNS requests. For more information, refer to Consul DNS views for Kubernetes.

Prerequisites

You must meet the following minimum application versions to enable the Consul DNS proxy for Kubernetes:

• Consul v1.20.0 or higher
• Either Consul on Kubernetes or the Consul Helm chart, v1.6.0 or higher

Update Helm values

To enable the Consul DNS proxy, add the required Helm values to your Consul on Kubernetes deployment.

connectInject:
  enabled: true
dns:
  enabled: true
  proxy: true

ACLs

We recommend you create a dedicated ACL token with DNS permissions for the Consul DNS proxy. The Consul DNS proxy requires these ACL permissions.

node_prefix "" {
  policy = "read"
}

service_prefix "" {
  policy = "read"
}

You can manage ACL tokens with Consul on Kubernetes, or you can configure the DNS proxy to access a token stored in Kubernetes secret. To use a Kubernetes secret, add the following configuration to your Helm chart.

dns:
  proxy:
    aclToken:
      secretName: <Consul-DNS-Token>
      secretKey: <Token-Value>

Retrieve Consul DNS proxy's address

To look up the IP address for the Consul DNS proxy in the Kubernetes Pod, run the following command.

$ kubectl get services –-all-namespaces --selector="app=consul,component=dns-proxy" --output jsonpath='{.spec.clusterIP}'  
10.96.148.46  

Use this address when you update the ConfigMap resource.

Update Kubernetes ConfigMap

Create or update a ConfigMap object in the Kubernetes cluster so that Kubernetes forwards DNS requests with the .consul domain to the IP address of the Consul DNS proxy.

The following example of a coredns-custom ConfigMap configures Kubernetes to forward Consul DNS requests in the cluster to the Consul DNS Proxy running on 10.96.148.46. This resource modifies the CoreDNS without modifications to the original Corefile.

kind: ConfigMap  
metadata:  
  name: coredns-custom  
  namespace: kube-system  
data:  
  consul.server: |  
    consul:53 {  
      errors  
      cache 30  
      forward . 10.96.148.46
      reload  
    }  

After updating the DNS configuration, perform a rolling restart of the CoreDNS.

kubectl -n kube-system rollout restart deployment coredns

For more information about using a coredns-custom resource, refer to the Rewrite DNS guide in the Azure documentation. For general information about modifying a ConfigMap, refer to the Kubernetes documentation.

Next steps

After you enable the Consul DNS proxy, services in the Kubernetes cluster can resolve Consul DNS addresses.

• To learn more about Consul DNS for service discovery, refer to DNS usage overview.
• If your datacenter has ACLs enabled, create a Consul ACL token for the Consul DNS proxy and then restart the DNS proxy.
• To enable service discovery across admin partitions, export services between partitions.
• To use Consul DNS for service discovery with other runtimes, across cloud regions, or between cloud providers, establish a cluster peering connection.