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run_in_existing_vpc.md

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Running in a shared VPC

When launching into a shared VPC, the VPC & the Internet Gateway will be reused. By default we create a new subnet per zone, and a new route table, but you can also use a shared subnet (see below).

  1. Use kops create cluster with the --vpc argument for your existing VPC:
export KOPS_STATE_STORE=s3://<somes3bucket>
export CLUSTER_NAME=<sharedvpc.mydomain.com>
export VPC_ID=vpc-12345678 # replace with your VPC id
export NETWORK_CIDR=10.100.0.0/16 # replace with the cidr for the VPC ${VPC_ID}

kops create cluster --zones=us-east-1b --name=${CLUSTER_NAME} --vpc=${VPC_ID}
  1. Then kops edit cluster ${CLUSTER_NAME} will show you something like:
metadata:
  creationTimestamp: "2016-06-27T14:23:34Z"
  name: ${CLUSTER_NAME}
spec:
  cloudProvider: aws
  networkCIDR: ${NETWORK_CIDR}
  networkID: ${VPC_ID}
  nonMasqueradeCIDR: 100.64.0.0/10
  subnets:
  - cidr: 172.20.32.0/19
    name: us-east-1b
    type: Public
    zone: us-east-1b

Verify that networkCIDR & networkID match your VPC CIDR & ID. You likely need to set the CIDR on each of the Zones, because subnets in a VPC cannot overlap.

  1. You can then run kops update cluster in preview mode (without --yes). You don't need any arguments, because they're all in the cluster spec:
kops update cluster ${CLUSTER_NAME}

Review the changes to make sure they are OK - the Kubernetes settings might not be ones you want on a shared VPC (in which case, open an issue!)

Note also the Kubernetes VPCs (currently) require EnableDNSHostnames=true. kops will detect the required change, but refuse to make it automatically because it is a shared VPC. Please review the implications and make the change to the VPC manually.

  1. Once you're happy, you can create the cluster using:
kops update cluster ${CLUSTER_NAME} --yes

This will add an additional Tag to your aws vpc resource. This tag will be removed automatically if you delete your kops cluster.

"kubernetes.io/cluster/<cluster-name>" = "shared"

Prior to kops 1.8 this Tag Key was KubernetesCluster which is obsolete and should not be used anymore as it only supports one cluster.

VPC with multiple CIDRs

AWS now allows you to add more CIDRs to a VPC, the param additionalNetworkCIDRs allows you to specify any additional CIDRs added to the VPC.

metadata:
  creationTimestamp: "2016-06-27T14:23:34Z"
  name: ${CLUSTER_NAME}
spec:
  cloudProvider: aws
  networkCIDR: 10.1.0.0/16
  additionalNetworkCIDRs:
  - 10.2.0.0/16
  networkID: vpc-00aa5577
  subnets:
  - cidr: 10.1.0.0/19
    name: us-east-1b
    type: Public
    zone: us-east-1b
    id: subnet-1234567
  - cidr: 10.2.0.0/19
    name: us-east-1b
    type: Public
    zone: us-east-1b
    id: subnet-1234568

Advanced Options for Creating Clusters in Existing VPCs

Shared Subnets

kops can create a cluster in shared subnets in both public and private network topologies. Doing so is not recommended unless you are using external networking

  1. Use kops create cluster with the --subnets argument for your existing subnets:
export KOPS_STATE_STORE=s3://<somes3bucket>
export CLUSTER_NAME=<sharedvpc.mydomain.com>
export VPC_ID=vpc-12345678 # replace with your VPC id
export NETWORK_CIDR=10.100.0.0/16 # replace with the cidr for the VPC ${VPC_ID}
export SUBNET_ID=subnet-12345678 # replace with your subnet id
export SUBNET_CIDR=10.100.0.0/24 # replace with your subnet CIDR
export SUBNET_IDS=$SUBNET_IDS # replace with your comma separated subnet ids

kops create cluster --zones=us-east-1b --name=${CLUSTER_NAME} --subnets=${SUBNET_IDS}

--vpc is optional when specifying --subnets. When creating a cluster with a private topology and shared subnets, the utility subnets should be specified similarly with --utility-subnets.

  1. Then kops edit cluster ${CLUSTER_NAME} will show you something like:
metadata:
  creationTimestamp: "2016-06-27T14:23:34Z"
  name: ${CLUSTER_NAME}
spec:
  cloudProvider: aws
  networkCIDR: ${NETWORK_CIDR}
  networkID: ${VPC_ID}
  nonMasqueradeCIDR: 100.64.0.0/10
  subnets:
  - cidr: ${SUBNET_CIDR}
    id: ${SUBNET_ID}
    name: us-east-1b
    type: Public
    zone: us-east-1b
  1. Once you're happy, you can create the cluster using:
kops update cluster ${CLUSTER_NAME} --yes

Subnet Tags

By default, kops will tag your existing subnets with the standard tags:

Public/Utility Subnets:

"kubernetes.io/cluster/<cluster-name>" = "shared"
"kubernetes.io/role/elb"               = "1"
"SubnetType"                           = "Utility"

Private Subnets:

"kubernetes.io/cluster/<cluster-name>" = "shared"
"kubernetes.io/role/internal-elb"      = "1"
"SubnetType"                           = "Private"

These tags are important, for example, your services will be unable to create public or private Elastic Load Balancers (ELBs) if the respective elb or internal-elb tags are missing.

If you would like to manage these tags externally then specify --disable-subnet-tags during your cluster creation. This will prevent kops from tagging existing subnets and allow some custom control, such as separate subnets for internal ELBs.

Prior to kops 1.8 KubernetesCluster tag was used instead of kubernetes.io/cluster/<cluster-name>. This lead to several problems if there were more than one Kubernetes Cluster in a subnet. After you upgraded to kops 1.8 ensure the KubernetesCluster Tag is removed from subnets otherwise kubernetes.io/cluster/<clustername> won't have any effect!

Shared NAT Egress

On AWS in private topology, kops creates one NAT Gateway (NGW) per AZ. If your shared VPC is already set up with an NGW in the subnet that kops deploys private resources to, it is possible to specify the ID and have kops/kubernetes use it.

If you don't want to use NAT Gateways but have setup EC2 NAT Instances in your VPC that you can share, it's possible to specify the IDs of said instances and have kops/kubernetes use them.

After creating a basic cluster spec, edit your cluster to specify NGW:

kops edit cluster ${CLUSTER_NAME}

spec:
  subnets:
  - cidr: 10.20.64.0/21
    name: us-east-1a
    egress: nat-987654321
    type: Private
    zone: us-east-1a
  - cidr: 10.20.96.0/21
    name: us-east-1b
    egress: i-987654321
    type: Private
    zone: us-east-1a
  - cidr: 10.20.32.0/21
    name: utility-us-east-1a
    type: Utility
    zone: us-east-1a

Please note:

  • You must specify pre-create subnets for all the subnets, or for none of them.
  • kops won't alter your existing subnets. Therefore they must be correctly set up with route tables etc. The Public or Utility subnets should have public IPs and an internet gateway configured as their default route in their route table. Private subnets should not have public IPs, and will typically have a NAT gateway configured as their default route.
  • kops won't create a route-table at all if we're not creating subnets.
  • In the example above the first subnet is using a shared NAT Gateway while the second one is using a shared NAT Instance

Proxy VPC Egress

See HTTP Forward Proxy Support