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. The TTL of the records can be set with the external-dns.alpha.kubernetes.io/ttl node annotation. The FQDN template provides more than 100+ functions, documented here. For instance, it includes a function to replace all . with - in the node name, which can be useful with cloud providers that include dots in the node name. There are two additional functions available on top of the standard sprig functions: isIPv4 and isIPv6. The functions can be used to test a string for being an IPv4 or IPv6 address.

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

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:v0.15.1
        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 | replace "." "-"}}.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:v0.15.1
        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 | replace "." "-"}}.external-dns-test.my-org.com
        - --txt-owner-id=my-identifier
        - --policy=sync
        - --log-level=debug