F5 Networks VirtualServer Source

This tutorial describes how to configure ExternalDNS to use the F5 Networks VirtualServer Source. It is meant to supplement the other provider-specific setup tutorials.

The F5 Networks VirtualServer CRD is part of this project. See more in-depth info regarding the VirtualServer CRD in the official documentation.

Start with ExternalDNS with the F5 Networks VirtualServer source

1. Make sure that you have the k8s-bigip-ctlr installed in your cluster. The needed CRDs are bundled within the controller.

2. In your Helm values.yaml add:

sources:
  - ...
  - f5-virtualserver
  - ...

or add it in your Deployment if you aren't installing external-dns via Helm:

args:
- --source=f5-virtualserver

Note that, in case you're not installing via Helm, you'll need the following in the ClusterRole bound to the service account of external-dns:

- apiGroups:
  - cis.f5.com
  resources:
  - virtualservers
  verbs:
  - get
  - list
  - watch

How it works

The F5 VirtualServer source creates DNS records based on the following fields:

• spec.host: The primary hostname for the virtual server
• spec.hostAliases: Additional hostnames that should also resolve to the same targets
• spec.virtualServerAddress: The IP address to use as the target (if no target annotation is set)
• status.vsAddress: The IP address from the status field (if no spec address or target annotation is set)

Example VirtualServer with hostAliases

apiVersion: cis.f5.com/v1
kind: VirtualServer
metadata:
  name: example-vs
  namespace: default
spec:
  host: www.example.com
  hostAliases:
    - alias1.example.com
    - alias2.example.com
  virtualServerAddress: 192.168.1.100

This configuration will create DNS A records for:

• www.example.com → 192.168.1.100
• alias1.example.com → 192.168.1.100
• alias2.example.com → 192.168.1.100

Target Priority

The source follows this priority order for determining targets:

1. Target annotation: external-dns.alpha.kubernetes.io/target (highest priority)
2. Spec address: spec.virtualServerAddress
3. Status address: status.vsAddress

If none of these are available, the VirtualServer will be skipped.

TTL Support

You can set a custom TTL using the annotation:

annotations:
  external-dns.alpha.kubernetes.io/ttl: "300"

Annotation Filtering

You can filter VirtualServers using the --annotation-filter flag to only process those with specific annotations.