By default each cluster created with Kubermatic gets the following network settings:
As a cluster grows over time it might become necessary to increase the above CIDR’s.
When creasing the CIDR, the new CIDR must include the old one - it is not possible to use a different network.
To change the service CIDR, edit the cluster object and specify the new CIDR:
clusterNetwork: dnsDomain: cluster.local pods: cidrBlocks: - 172.25.0.0/16 services: cidrBlocks: - 10.10.10.0/24
clusterNetwork: dnsDomain: cluster.local pods: cidrBlocks: - 172.25.0.0/16 services: cidrBlocks: - 10.10.0.0/16
After the CIDR has been changed, all new services will get an IP from the new CIDR.
This might cause a downtime of the cluster DNS & communication to the API server
Kubermatic will always create a Service with a static ClusterIP for the DNS service(
The ClusterIP will always be the 10th of the network.
Example: Give the service CIDR:
10.10.10.0/24, the Service for the DNS will have the ClusterIP
When the CIDR gets changed, the DNS service(
kube-system/kube-dns) must be changed as well.
As changing the ClusterIP is not possible, the Service(
kube-system/kube-dns) must be recreated (A backup must be created):
# Dump old service kubectl -n kube-system get service kube-dns -o yaml > old_service.yaml # Delete old service kubectl -n kube-system delete service kube-dns # Kubermatic will recreate it with the new IP # Create old service with a different name to not break existing DNS # For this change metadata.name inside old_service.yaml and apply it kubectl apply -f old_service.yaml # Delete the kubernetes service kubectl delete service kubernetes # Wait until it gets recreated