<p>I'm initiating a kubernetes cluster with:</p>

<pre><code>kubeadm init --pod-network-cidr=192.168.1.0/16 --apiserver-advertise-address=192.168.0.33
</code></pre>

<p>I'm not too familiar with networking concepts or CIDR, how do I determine an appropriate value for the pod CIDR?</p>

<p>I previously used <code>10.244.0.0/16</code> but that resulted in:</p>

<pre><code>Failed create pod sandbox: rpc error: code = Unknown desc = failed to set up sandbox container "78cf556b2e87e15cc5ec8827ca3a397c16dcfb90f045e225a17028f072db6e5f" network for pod "coredns-78fcdf6894-c7kq2": NetworkPlugin cni failed to set up pod "coredns-78fcdf6894-c7kq2_kube-system" network: failed to set bridge addr: "cni0" already has an IP address different from 10.244.1.1/24
</code></pre>

<p>Regarding CIDR (<code>Classless Inter-Domain Routing</code>): That is just a notation to define the subnet / range of IP addresses that you want to use in your network.</p>

<p>If you want to use <code>/16</code>, you must be planning the creation of a fairly big Kubernetes cluster since that will give you <code>&gt;65k</code> virtual IP addresses (Note that we are talking about the SDN / Virtual network, i.e., the IPs you will set for your kubernetes PODs, not your actual nodes / hosts).
Here is a CIDR table you can use as reference to decide a more suitable range:
<a href="https://kb.wisc.edu/ns/page.php?id=3493" rel="noreferrer">https://kb.wisc.edu/ns/page.php?id=3493</a></p>

<p>Now, in terms of your failure that depends on the CNI (<code>Container Networking Interface</code>) plugin you are using in your Kubernetes cluster. If you are using the default one that must be <code>Kubenet</code>, which has limitations.
More information here:
<a href="https://kubernetes.io/docs/concepts/extend-kubernetes/compute-storage-net/network-plugins/" rel="noreferrer">https://kubernetes.io/docs/concepts/extend-kubernetes/compute-storage-net/network-plugins/</a>
and here:
<a href="https://chrislovecnm.com/kubernetes/cni/choosing-a-cni-provider/" rel="noreferrer">https://chrislovecnm.com/kubernetes/cni/choosing-a-cni-provider/</a></p>

<p>I hope that helps.</p>
