How can I modify the CIDR block on my VPC to accommodate more hosts?

Last updated: 2019-08-22

I can't create new resources on my Amazon Virtual Private Cloud (Amazon VPC) because the IP address space provided by the CIDR block assigned to my Amazon VPC is depleted. How can I modify my CIDR block to accommodate more hosts?

Resolution

After you create a CIDR block, you can't resize it. However, you can make other modifications to accommodate additional hosts.

To understand your options, first determine whether your depleted CIDR block is a primary or secondary CIDR block:

  1. Open the Amazon VPC console.
  2. Choose Your VPCs.
  3. Select your VPC.
  4. Review the entries under CIDR blocks. The first entry is the primary CIDR block.

If your depleted CIDR block is a secondary CIDR block, complete one of the following:

If your depleted CIDR block is the primary CIDR block, you can’t disassociate it. Instead, complete one of the following:

By default, a local route is added to all routing tables in the VPC for every CIDR block associated with the VPC. This enables you to route traffic between the primary and secondary CIDR resources without additional routing. To restrict unintended traffic, use security groups and network access control lists (ACLs).


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