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Multi-Cluster Networking

From v1.4.0, two or more Kubernetes clusters can be connected with each other. Pods in different clusters can communicate directly using Pod IP. Kub-OVN uses tunnel to encapsulate traffic between clusters gateways, only L3 connectivity for gateway nodes is required.

Prerequest

  • To use route auto advertise, subnet CIDRs in different clusters MUST NOT be overlapped with each other，including ovn-default and join subnets CIDRs. Otherwise, you should disable the auto route and add routes mannually.
  • The Interconnection Controller SHOULD be deployed in a region that every cluster can access by IP.
  • Every cluster SHOULD have at least one node(work as gateway later) that can access other gateway nodes in different clusters by IP.
  • Cluster interconnection network now CANNOT work together with SNAT and EIP functions.

Auto Route Step

  1. Run Interconnection Controller in a region that can be accessed by other cluster
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:v1.7.1 bash start-ic-db.sh

​ If containerd replaces docker then the command is as follows:

ctr run  -d --net-host --mount="type=bind,src=/etc/ovn/,dst=/etc/ovn,options=rbind:rw" --mount="type=bind,src=/var/run/ovn,dst=/var/run/ovn,options=rbind:rw" --mount="type=bind,src=/var/log/ovn,dst=/var/log/ovn,options=rbind:rw"  kubeovn/kube-ovn:v1.7.1 ovn-ic-db bash start-ic-db.sh
  1. Create ovn-ic-config ConfigMap in each cluster kube-system namespace. Edit and apply the yaml below in each cluster.
apiVersion: v1
kind: ConfigMap
metadata:
  name: ovn-ic-config
  namespace: kube-system
data:
  enable-ic: "true"
  az-name: "az1"                # AZ name for cluster, every cluster should be different
  ic-db-host: "192.168.65.3"    # The Interconnection Controller host IP address
  ic-nb-port: "6645"            # The ic-nb port, default 6645
  ic-sb-port: "6646"            # The ic-sb port, default 6646
  gw-nodes: "az1-gw"            # The node name which acts as the interconnection gateway
  auto-route: "true"            # Auto announce route to all clusters. If set false, you can select announced routes later manually
  1. Check if interconnection is established.
## In Interconnection Controller container
[root@ic]# ovn-ic-sbctl show
availability-zone az1
    gateway deee03e0-af16-4f45-91e9-b50c3960f809
        hostname: az1-gw
        type: geneve
            ip: 192.168.42.145
        port ts-az1
            transit switch: ts
            address: ["00:00:00:50:AC:8C 169.254.100.45/24"]
availability-zone az2
    gateway e94cc831-8143-40e3-a478-90352773327b
        hostname: az2-gw
        type: geneve
            ip: 192.168.42.149
        port ts-az2
            transit switch: ts
            address: ["00:00:00:07:4A:59 169.254.100.63/24"]

## In each cluster
[root@az1 ~]# kubectl ko nbctl lr-route-list ovn-cluster
IPv4 Routes
                10.42.1.1            169.254.100.45 dst-ip (learned)
                10.42.1.3                100.64.0.2 dst-ip
                10.16.0.2                100.64.0.2 src-ip
                10.16.0.3                100.64.0.2 src-ip
                10.16.0.4                100.64.0.2 src-ip
                10.16.0.6                100.64.0.2 src-ip
             10.17.0.0/16            169.254.100.45 dst-ip (learned)
            100.65.0.0/16            169.254.100.45 dst-ip (learned)

If Pods cannot communicate with each other, please check the log of kube-ovn-controller.

For some specific subnet that you don't want to advertise to another cluster, you can disable the auto route advertise on the specific subnet by editing the subnet spec.

apiVersion: kubeovn.io/v1
kind: Subnet
metadata:
  name: no-advertise
spec:
  cidrBlock: 10.199.0.0/16
  disableInterConnection: false

For manually adding routes, you need to find the

Manually Route Step

  1. Same as AutoRoute step 1,run Interconnection Controller in a region that can be accessed by other cluster
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:v1.7.1 bash start-ic-db.sh
  1. Create ic-config ConfigMap in each cluster. Edit and apply the yaml below in each cluster. Note that auto-route is set to false
apiVersion: v1
kind: ConfigMap
metadata:
  name: ovn-ic-config
  namespace: kube-system
data:
  enable-ic: "true"
  az-name: "az1"                # AZ name for cluster, every cluster should be different
  ic-db-host: "192.168.65.3"    # The Interconnection Controller host IP address
  ic-nb-port: "6645"            # The ic-nb port, default 6645
  ic-sb-port: "6646"            # The ic-sb port, default 6646
  gw-nodes: "az1-gw"            # The node name which acts as the interconnection gateway
  auto-route: "false"           # Auto announce route to all clusters. If set false, you can select announced routes later manually
  1. Find the remote gateway address in each cluster, and add routes to remote cluster.

In az1

[root@az1 ~]# kubectl ko nbctl show
switch a391d3a1-14a0-4841-9836-4bd930c447fb (ts)
    port ts-az1
        type: router
        router-port: az1-ts
    port ts-az2
        type: remote
        addresses: ["00:00:00:4B:E2:9F 169.254.100.31/24"]

In az2

[root@az2 ~]# kubectl ko nbctl show
switch da6138b8-de81-4908-abf9-b2224ec4edf3 (ts)
    port ts-az2
        type: router
        router-port: az2-ts
    port ts-az1
        type: remote
        addresses: ["00:00:00:FB:2A:F7 169.254.100.79/24"]

Record the remote lsp address in ts logical switch

  1. Add Static route in each cluster

In az1

kubectl ko nbctl lr-route-add ovn-cluster 10.17.0.0/24 169.254.100.31

In az2

 kubectl ko nbctl lr-route-add ovn-cluster 10.16.0.0/24 169.254.100.79

Gateway High Available

Kube-OVN now supports Active-Backup mode gateway HA. You can add more nodes name in the configmap separated by commas.

Active-Active mode gateway HA is under development.