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Re: NetworkCIDR for big cluster





On Oct 6, 2016, at 1:23 PM, Srinivas Naga Kotaru (skotaru) <skotaru cisco com> wrote:

Hi

 

We ‘re building 3 big clusters, 1 specific to each data center. growth  expected to 1000 nodes each cluster over the time.

 

Questions:

 

1.        

# egrep 'clusterNetworkCIDR|serviceNetworkCIDR' /etc/origin/master/master-config.yaml

 

  clusterNetworkCIDR: 10.1.0.0/16

  serviceNetworkCIDR: 172.30.0.0/16

 

above are default subnet values.  These defaults will be sufficient for 1k clsuter size?


That would be 64k pods and services.  If you expect densities in excess of 100 pods per node you should probably plan for a larger cidr for the cluster network and if you are using the multi tenant plugin you'll also want to plan around how many unique projects you will have.

So inputs are:
# of projects
Expected number of services per project (simple apps or complex apps per project)
Expected pod densities per node


 

2.       if answer is ‘no’ can we change once cluster is build with new CIDR values depending on growth? ( I heard it is not possible once cluster was build)



It is possible to grow it if you include the original cidr in the expanded cidr.  However, it can be disruptive so we recommend planning up front.  I would recommend leaving the possibility of a larger block open by expanding the mask if you are unsure about exact limits.


3.       if answer is ‘no’ what is the right CIDR’s for 1k cluster size?

 

 

-- 

Srinivas Kotaru

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