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VPC CIDR Blocks

Learn how VPCs use CIDR notation to define address ranges

CoreWeave VPCs use Classless Inter-Domain Routing (CIDR) notation to define IP address ranges for the hosts, Pods, Load Balancers, and other Services used in each VPC.

Understanding CIDR blocks is especially useful for customers who need to know IP ranges in advance of integrating with existing environments, such as with Direct Connect.

When planning your network architecture, ensure that you allocate sufficient IP addresses to accommodate your Nodes and their associated services. To convert CIDRs to IP address ranges, we recommend using the ARIN CIDR Calculator.

Configuring CIDR blocks in VPCs​

Below is an example YAML configuration for a single VPC containing multiple clusters, indicating the assignment of different CIDR ranges for different resources:

Example vpc.yaml
organizations:

  abc123:

    vpcs:

      default-us-east-04:

        hostPrefixes:

          - 10.176.192.0/18

        pubImport: true

        site: us-east-04

    clusters:

      poc-gpu:

        version: v1.30

        site: us-east-04

        vpc: default-us-east-04

        podCIDR: 10.24.0.0/13

        serviceCIDR: 10.32.0.0/22

        internalLbCIDR: 10.32.4.0/22

      poc-cpu:

        version: v1.30

        site: us-east-04

        vpc: default-us-east-04

        podCIDR: 10.48.0.0/13

        serviceCIDR: 10.56.0.0/22

        internalLbCIDR: 10.56.4.0/22

CIDR block size guidelines​

CIDR blocks for Nodes, Pods, Services, and Load Balancers have different subnet allocation limits. The following guidelines are based on the maximum number of resources that can be accommodated in each CIDR block:

KeyValueDescription
hostPrefixes/18An /18 CIDR block accommodates clusters with up to 4,000 Nodes. Each Node requires 2 IP addresses.
podCIDR/13A /13 CIDR block allows up to 100 Pods per Node.
serviceCIDR/22A /22 CIDR block allows up to 1000 Services.
internalLbCIDR/22A /22 CIDR block allows up to 1000 Load Balancers.
Info

Customers with smaller environments may be able to use smaller CIDR ranges. For example, if the cluster is planned to have only 500 Nodes, a large CIDR block isn't required - however, using smaller CIDR ranges may limit future expansion, as Service IPs must be contiguous.

Planning CIDRs for connected VPCs​

When connecting two CoreWeave Virtual Private Clouds (VPCs) between CKS clusters, make sure to plan unique, non-overlapping address space across the clusters. At a minimum, the two clusters must have non-overlapping internal Load Balancer CIDR blocks. To simplify routing between VPCs, the best practice is to ensure that all CIDR ranges used by each cluster, such as the Pod, Service, and Load Balancer CIDR, are non-overlapping.

Set non-overlapping CIDR ranges when you create or edit each VPC in the Cloud Console. For the configuration flow, see Create and Manage VPCs. For automation, you can provision VPCs and their prefixes using the VPC API (for example, using the hostPrefix and vpcPrefixes fields).

If you use Liqo for multi-cluster networking, its network fabric prefers NAT-less communication when PodCIDRs are disjoint, and applies address translation only when overlaps exist.

Additional resources​

How-to guides​

References​

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