Add comment clarifying network allocation and sizes (#6607)

* Add comment from roles/kubespray-defaults/defaults/main.yaml clarifying network allocation and sizes

Signed-off-by: Mikael Johansson <mik.json@gmail.com>

* Rewrite of the comment and added new examples

Signed-off-by: Mikael Johansson <mik.json@gmail.com>

inventory/sample/group_vars/k8s-cluster/k8s-cluster.yml

@@ -95,8 +95,20 @@ kube_service_addresses: 10.233.0.0/18
 kube_pods_subnet: 10.233.64.0/18
 
 # internal network node size allocation (optional). This is the size allocated
-# to each node on your network.  With these defaults you should have
-# room for 4096 nodes with 254 pods per node.
+# to each node for pod IP address allocation. Note that the number of pods per node is
+# also limited by the kubelet_max_pods variable which defaults to 110.
+#
+# Example:
+# Up to 64 nodes and up to 254 or kubelet_max_pods (the lowest of the two) pods per node:
+#  - kube_pods_subnet: 10.233.64.0/18
+#  - kube_network_node_prefix: 24
+#  - kubelet_max_pods: 110
+#
+# Example:
+# Up to 128 nodes and up to 126 or kubelet_max_pods (the lowest of the two) pods per node:
+#  - kube_pods_subnet: 10.233.64.0/18
+#  - kube_network_node_prefix: 25
+#  - kubelet_max_pods: 110
 kube_network_node_prefix: 24
 
 # The port the API Server will be listening on.

roles/kubespray-defaults/defaults/main.yaml

@@ -174,16 +174,20 @@ kube_service_addresses: 10.233.0.0/18
 kube_pods_subnet: 10.233.64.0/18
 
 # internal network node size allocation (optional). This is the size allocated
-# to each node on your network.  With these defaults you should have
-# room for 64 nodes with 254 pods per node.
-# Example: Up to 256 nodes, 100 pods per node (/16 network):
-#  - kube_service_addresses: 10.233.0.0/17
-#  - kube_pods_subnet: 10.233.128.0/17
-#  - kube_network_node_prefix: 25
-# Example: Up to 4096 nodes, 100 pods per node (/12 network):
-#  - kube_service_addresses: 10.192.0.0/13
-#  - kube_pods_subnet: 10.200.0.0/13
+# to each node for pod IP address allocation. Note that the number of pods per node is
+# also limited by the kubelet_max_pods variable which defaults to 110.
+#
+# Example:
+# Up to 64 nodes and up to 254 or kubelet_max_pods (the lowest of the two) pods per node:
+#  - kube_pods_subnet: 10.233.64.0/18
+#  - kube_network_node_prefix: 24
+#  - kubelet_max_pods: 110
+#
+# Example:
+# Up to 128 nodes and up to 126 or kubelet_max_pods (the lowest of the two) pods per node:
+#  - kube_pods_subnet: 10.233.64.0/18
 #  - kube_network_node_prefix: 25
+#  - kubelet_max_pods: 110
 kube_network_node_prefix: 24
 
 # The virtual cluster IP, real host IPs and ports the API Server will be