Can pod-network-cidr and service-cidr overlap outside cluster intranet ips?

General Discussions
1

Hello, guys! i have a few questions about the pod-network-cidr and service-cidr and maybe someone can help me to understand.

Are these pod-network-cidr and service-cidr internal to the kubernetes cluster only ? Can they interfere with the external network if those addresses overlap addresses outside the cluster ?
Hypothetically speaking, since service-cidr defaults to “10.96.0.0/12”, what would happen if somewhere in my network ( outside the k8s cluster ) i have a router whose ip is 10.111.255.254 ( that belongs to the 10.96.0.0/12) ?
Thanks for the help!

2

Hi! We looked at this question during office hours, take a look!

3

here are the result:
https://kubernetes.io/docs/setup/independent/create-cluster-kubeadm/#pod-network

that your Pod network must not overlap with any of the host networks as this can cause issues. If you find a collision between your network plugin’s preferred Pod network and some of your host networks, you should think of a suitable CIDR replacement and use that during kubeadm init with --pod-network-cidr and as a replacement in your network plugin’s YAML.

4

I would love to understand this! if the pod and services CIDR are virtual networks and internal to the cluster, what would be the issue if they overlap with an external non-cluster network? especially onprem?