nodes.md

Cluster Nodes as Source

This tutorial describes how to configure ExternalDNS to use the cluster nodes as source. Using nodes (--source=node) as source is possible to synchronize a DNS zone with the nodes of a cluster.

The node source adds an A record per each node externalIP (if not found, any IPv4 internalIP is used instead). It also adds an AAAA record per each node IPv6 internalIP. Refer to the IPv6 Behavior section for more details. The TTL of the records can be set with the external-dns.alpha.kubernetes.io/ttl node annotation.

Nodes marked as Unschedulable as per core/v1/NodeSpec are excluded. This avoid exposing Unhealthy, NotReady or SchedulingDisabled (cordon) nodes.

IPv6 Behavior

By default, ExternalDNS exposes the IPv6 InternalIP of the nodes. To prevent this, you can use the --no-expose-internal-ipv6 flag. The default behavior will change in the next minor release. ExternalDNS will no longer expose the IPv6 InternalIP addresses by default. You can still explicitly expose the internal ipv6 addresses by using the --expose-internal-ipv6 flag, if needed.

Example spec (without exposing IPv6 InternalIP addresses)

spec:
  serviceAccountName: external-dns
  containers:
  - name: external-dns
    image: registry.k8s.io/external-dns/external-dns:v0.16.1 # update this to the desired external-dns version
    args:
    - --source=node # will use nodes as source
    - --provider=aws
    - --zone-name-filter=external-dns-test.my-org.com # will make ExternalDNS see only the hosted zones matching provided domain, omit to process all available hosted zones
    - --domain-filter=external-dns-test.my-org.com
    - --aws-zone-type=public
    - --registry=txt
    - --fqdn-template={{.Name}}.external-dns-test.my-org.com
    - --txt-owner-id=my-identifier
    - --policy=sync
    - --log-level=debug
    - --no-expose-internal-ipv6

Manifest (for cluster without RBAC enabled)

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: external-dns
spec:
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: external-dns
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      serviceAccountName: external-dns
      containers:
      - name: external-dns
        image: registry.k8s.io/external-dns/external-dns:v0.16.1
        args:
        - --source=node # will use nodes as source
        - --provider=aws
        - --zone-name-filter=external-dns-test.my-org.com # will make ExternalDNS see only the hosted zones matching provided domain, omit to process all available hosted zones
        - --domain-filter=external-dns-test.my-org.com
        - --aws-zone-type=public
        - --registry=txt
        - --fqdn-template={{.Name}}.external-dns-test.my-org.com
        - --txt-owner-id=my-identifier
        - --policy=sync
        - --log-level=debug

Manifest (for cluster with RBAC enabled)

apiVersion: v1
kind: ServiceAccount
metadata:
  name: external-dns
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: external-dns
rules:
- apiGroups: ["route.openshift.io"]
  resources: ["routes"]
  verbs: ["get", "watch", "list"]
- apiGroups: [""]
  resources: ["services","endpoints","pods"]
  verbs: ["get","watch","list"]
- apiGroups: ["extensions","networking.k8s.io"]
  resources: ["ingresses"]
  verbs: ["get","watch","list"]
- apiGroups: [""]
  resources: ["nodes"]
  verbs: ["get", "watch", "list"]
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: external-dns-viewer
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: external-dns
subjects:
- kind: ServiceAccount
  name: external-dns
  namespace: external-dns
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: external-dns
spec:
  strategy:
    type: Recreate
  selector:
    matchLabels:
      app: external-dns
  template:
    metadata:
      labels:
        app: external-dns
    spec:
      serviceAccountName: external-dns
      containers:
      - name: external-dns
        image: registry.k8s.io/external-dns/external-dns:v0.16.1
        args:
        - --source=node # will use nodes as source
        - --provider=aws
        - --zone-name-filter=external-dns-test.my-org.com # will make ExternalDNS see only the hosted zones matching provided domain, omit to process all available hosted zones
        - --domain-filter=external-dns-test.my-org.com
        - --aws-zone-type=public
        - --registry=txt
        - --fqdn-template={{.Name}}.external-dns-test.my-org.com
        - --txt-owner-id=my-identifier
        - --policy=sync
        - --log-level=debug