Cloudformation - Update CIDR Range in Stack WITHOUT Terminating All RDS, ELB's Instances

Question

My client is try to increase the number of IP's available on a particular subnet for changing their CIDR range. The environment provisioning involved is driven by CloudFormation almost entirely. Is there a way to gracefully change the CIDR range without having to rebuild the entire CloudFormation stack? Otherwise, the client will need to migrate data off of the RDS databases at least into the new stack with the expanded CIDR range.

Thanks

Accepted Answer

I think the best way to handle that is to add more subnets to the VPC. Exactly how they do that will depend on what their CF template looks like.

If the customer can't create any more subnets (i.e. because they've filled up the entire VPC's CIDR range) then the customer can add an additional CIDR block to the VPC, and then create the new subnets in that new range:

https://docs.aws.amazon.com/vpc/latest/userguide/VPC_Subnets.html#vpc-resize

Cloudformation - Update CIDR Range in Stack WITHOUT Terminating All RDS, ELB's Instances

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