Fixed Addresses¶

By default, Kube-OVN randomly assigns IPs and Macs based on the Subnet to which the Pod's Namespace belongs. For workloads that require fixed addresses, Kube-OVN provides multiple methods of fixing addresses depending on the scenario.

• Single Pod fixed IP/Mac.
• Workload IP Pool to specify fixed addresses.
• StatefulSet fixed address.
• KubeVirt VM fixed address.

Single Pod Fixed IP/Mac¶

You can specify the IP/Mac required for the Pod by annotation when creating the Pod. The kube-ovn-controller will skip the address random assignment phase and use the specified address directly after conflict detection, as follows:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: ippool
  labels:
    app: ippool
spec:
  replicas: 2
  selector:
    matchLabels:
      app: ippool
  template:
    metadata:
      labels:
        app: ippool
      annotations:
        ovn.kubernetes.io/ip_pool: 10.16.0.15,10.16.0.16,10.16.0.17 // for dualstack ippool use semicolon to separate addresses 10.16.0.15,fd00:10:16::000E;10.16.0.16,fd00:10:16::0
    spec:
      containers:
        - name: ippool
          image: docker.io/library/nginx:alpine

The following points need to be noted when using annotation.

1. The IP/Mac used cannot conflict with an existing IP/Mac.
2. The IP must be in the CIDR range of the Subnet it belongs to.
3. You can specify only IP or Mac. When you specify only one, the other one will be assigned randomly.

Workload IP Pool¶

Kube-OVN supports setting fixed IPs for Workloads (Deployment/StatefulSet/DaemonSet/Job/CronJob) via annotation ovn.kubernetes.io/ip_pool. kube-ovn-controllerr will automatically select the IP specified in ovn.kubernetes.io/ip_pool and perform conflict detection.

The Annotation of the IP Pool needs to be added to the annotation field in the template. In addition to Kubernetes built-in workload types, other user-defined workloads can also be assigned fixed addresses using the same approach.

Deployment With Fixed IPs¶

apiVersion: apps/v1
kind: Deployment
metadata:
  namespace: ls1
  name: starter-backend
  labels:
    app: starter-backend
spec:
  replicas: 2
  selector:
    matchLabels:
      app: starter-backend
  template:
    metadata:
      labels:
        app: starter-backend
      annotations:
        ovn.kubernetes.io/ip_pool: 10.16.0.15,10.16.0.16,10.16.0.17 // for dualstack ippool use semicolon to separate addresses 10.16.0.15,fd00:10:16::000E;10.16.0.16,fd00:10:16::000F;10.16.0.17,fd00:10:16::0010
    spec:
      containers:
      - name: backend
        image: docker.io/library/nginx:alpine

Using a fixed IP for Workload requires the following:

1. The IP in ovn.kubernetes.io/ip_pool should belong to the CIDR of the Subnet.
2. The IP in ovn.kubernetes.io/ip_pool cannot conflict with an IP already in use.
3. When the number of IPs in ovn.kubernetes.io/ip_pool is less than the number of replicas, the extra Pods will not be created. You need to adjust the number of IPs in ovn.kubernetes.io/ip_pool according to the update policy of the workload and the scaling plan.

StatefulSet Fixed Address¶

StatefulSet, like other workloads, can use ovn.kubernetes.io/ip_pool to specify the IP used by the Pod.

Since StatefulSet is mostly used for stateful services, which have higher requirements for fixed addresses, Kube-OVN has made special enhancements:

1. Pods are assigned IPs in ovn.kubernetes.io/ip_pool in order. For example, if the name of the StatefulSet is web, web-0 will use the first IP in ovn.kubernetes.io/ip_pool, web-1 will use the second IP, and so on.
2. The logical_switch_port in the OVN is not deleted during update or deletion of the StatefulSet Pod, and the newly generated Pod directly reuses the old logical port information. Pods can therefore reuse IP/Mac and other network information to achieve similar state retention as StatefulSet Volumes.
3. Based on the capabilities of 2, for StatefulSet without the ovn.kubernetes.io/ip_pool annotation, a Pod is randomly assigned an IP/Mac when it is first generated, and then the network information remains fixed for the lifetime of the StatefulSet.

StatefulSet Example¶

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  serviceName: "nginx"
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: docker.io/library/nginx:alpine
        ports:
        - containerPort: 80
          name: web

You can try to delete the Pod under StatefulSet to observe if the Pod IP changes.

KubeVirt VM Fixed Address¶

For VM instances created by KubeVirt, kube-ovn-controller can assign and manage IP addresses in a similar way to the StatefulSet Pod. This allows VM instances address fixed during start-up, shutdown, upgrade, migration, and other operations throughout their lifecycle, making them more compatible with the actual virtualization user experience.

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