Actually, that begs another question. The docs also specify that k8s
can support up to 5000 nodes. But I'm not clear on how the networking
can support that.
So let's go back to that service-cluster-ip-range with the /16 CIDR.
That only supports a maximum of 256 nodes.
Now the maximum size for the service-cluster-ip-range appears to be /12
- e.g., --service-cluster-ip-range=10.240.0.0/12 (Beyond that you get a
"Specified service-cluster-ip-range is too large" error.) So that means
12 bits for the high part of the address, and with each node taking the
lower 8 bits for the IP address of individual pods, that leaves 12
remaining bits worth of unique IP address ranges. 12 bits = 4095
possible IP addresses for nodes. How then could anyone scale up to 5000
nodes?
DR
On 2017-08-11 10:47 am, David Rosenstrauch wrote:
Ah. That makes a bit more sense.
Thanks!
DR
On 2017-08-11 10:41 am, Ben Kochie wrote:
Kuberentes will be giving a /24 to each node, not each pod. Each node
will give one IP out of that /24 to a pod it controls. This default
means you can have 253 pods-per-node. This of course can be adjust
depending on the size of your pods and nodes.
This means that you can fully utilize the /16 for pods (minus per-node
network, broadcast, gateway)
On Fri, Aug 11, 2017 at 4:36 PM, David Rosenstrauch
<dar...@darose.net> wrote:
According to the docs, k8s can support systems of up to 150000 pods.
(See https://kubernetes.io/docs/admin/cluster-large/ [1]) But
given k8s' networking model, I'm a bit puzzled on how that would
work.
It seems like a typical setup is to assign a
service-cluster-ip-range with a /16 CIDR. (Say 10.254.0.0/16 [2])
However, I notice that my cluster assigns a full /24 IP range to
each pod that it creates. (E.g., pod1 gets 10.254.1.*, pod2 gets
10.254.2.*, etc.) Given this networking setup, it would seem that
Kubernetes would only be capable of launching a maximum of 256 pods.
Am I misunderstanding how k8s works in this r? Or is it that the
networking would need to be configured differently to support more
than 256 pods?
Thanks,
DR
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