Integrating OpenStack and Kubernetes Networks with Kube-OVN: Cluster Interconnect and Shared OVN Modes

When you miss the rich networking capabilities of the SDN world while working in cloud‑native environments, Kube‑OVN provides a solution; this series introduces its advanced features and usage paths to help you solve container networking challenges.

Cluster Interconnect works like the OVN‑IC multi‑cluster interconnect method, but replaces the two cluster ends with OpenStack and Kubernetes. Prerequisites include non‑overlapping CIDRs, a set of machines reachable by both clusters for the interconnect controller, and designated gateway nodes.

Deploy OVN‑IC Database

docker run --name=ovn-ic-db -d --network=host \
  -v /etc/ovn/:/etc/ovn \
  -v /var/run/ovn:/var/run/ovn \
  -v /var/log/ovn:/var/log/ovn \
  kubeovn/kube-ovn:v1.10.6 bash start-ic-db.sh

Kubernetes Side Operations

Create a ConfigMap ovn-ic-config in the kube-system namespace with fields such as enable-ic , az-name , ic-db-host , ic-nb-port , ic-sb-port , gw-nodes , and auto-route :

apiVersion: v1
kind: ConfigMap
metadata:
  name: ovn-ic-config
  namespace: kube-system
data:
  enable-ic: "true"
  az-name: "az1"
  ic-db-host: "192.168.65.3"
  ic-nb-port: "6645"
  ic-sb-port: "6646"
  gw-nodes: "az1-gw"
  auto-route: "true"

OpenStack Side Operations

Create a logical router in OpenStack and set the availability zone name (different from other clusters):

# openstack router create router0

ovn-nbctl set NB_Global . name=op-az

Start the OVN‑IC controller pointing to the database:

/usr/share/ovn/scripts/ovn-ctl \
  --ovn-ic-nb-db=tcp:192.168.65.3:6645 \
  --ovn-ic-sb-db=tcp:192.168.65.3:6646 \
  --ovn-northd-nb-db=unix:/run/ovn/ovnnb_db.sock \
  --ovn-northd-sb-db=unix:/run/ovn/ovnsb_db.sock \
  start_ic

Configure the OVS bridge to act as an internet gateway:

ovs-vsctl set open_vswitch . external_ids:ovn-is-interconn=true

Set up logical router ports to connect the OpenStack router router0 with the interconnect switch ts and enable route advertisement and learning:

ovn-nbctl lrp-add router0 lrp-router0-ts 00:02:ef:11:39:4f 169.254.100.73/24
ovn-nbctl lsp-add ts lsp-ts-router0 -- lsp-set-addresses lsp-ts-router0 router -- lsp-set-type lsp-ts-router0 router -- lsp-set-options lsp-ts-router0 router-port=lrp-router0-ts
ovn-nbctl lrp-set-gateway-chassis lrp-router0-ts {gateway chassis} 1000
ovn-nbctl set NB_Global . options:ic-route-adv=true options:ic-route-learn=true

Verify learned Kubernetes routes:

# ovn-nbctl lr-route-list router0

Shared Underlying OVN

In this mode, OpenStack and Kubernetes share the same OVN instance, aligning VPC and Subnet concepts for tighter control. OpenStack must use networking-ovn as the Neutron backend.

Neutron Configuration Changes

Edit /etc/neutron/plugins/ml2/ml2_conf.ini to point to the OVN central nodes:

[ovn]
ovn_nb_connection = tcp:[192.168.137.176]:6641,tcp:[192.168.137.177]:6641,tcp:[192.168.137.178]:6641
ovn_sb_connection = tcp:[192.168.137.176]:6642,tcp:[192.168.137.177]:6642,tcp:[192.168.137.178]:6642
ovn_l3_scheduler = OVN_L3_SCHEDULER

Update each node’s OVS configuration:

ovs-vsctl set open . external-ids:ovn-remote=tcp:[192.168.137.176]:6642,tcp:[192.168.137.177]:6642,tcp:[192.168.137.178]:6642
ovs-vsctl set open . external-ids:ovn-encap-type=geneve
ovs-vsctl set open . external-ids:ovn-encap-ip=192.168.137.200

Using OpenStack Resources in Kubernetes

Query existing OpenStack resources (router, network, subnet, server) and the synchronized VPC in Kubernetes:

# openstack router list
# openstack network list
# openstack subnet list
# openstack server list
# kubectl get vpc

Create a namespace, bind it to the imported VPC, define a subnet, and launch a pod:

apiVersion: v1
kind: Namespace
metadata:
  name: net2
---
apiVersion: kubeovn.io/v1
kind: Vpc
metadata:
  name: neutron-22040ed5-0598-4f77-bffd-e7fd4db47e93
spec:
  namespaces:
  - net2
---
apiVersion: kubeovn.io/v1
kind: Subnet
metadata:
  name: net2
spec:
  vpc: neutron-22040ed5-0598-4f77-bffd-e7fd4db47e93
  cidrBlock: 12.0.1.0/24
  natOutgoing: false
---
apiVersion: v1
kind: Pod
metadata:
  name: ubuntu
  namespace: net2
spec:
  containers:
  - name: ubuntu
    image: kubeovn/kube-ovn:v1.8.0
    command: ["sleep", "604800"]
    imagePullPolicy: IfNotPresent
  restartPolicy: Always

For more details, refer to the official Kube‑OVN documentation at https://kubeovn.github.io/docs/v1.10.x/ .