Is the RAM share limit "the" limit for how many accounts a VPC can be RAM shared to?

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I support an organization with many hundreds of AWS Accounts. We use RAM (via AWS Organizations OUs) to share VPC subnets to accounts. In this case a VPC is hosted in one account, and then RAM shared to many accounts. My question is how to understand the limit to how many accounts an individual VPC can be shared.

I can find no explicit documentation saying "A VPC can be shared to up to X accounts".

But I do find RAM Share quota limits: RAM Share Service Quota

So assuming an individual resource share contained multiple subnets, then the first limit I would hit would be the max number of shared resources per AWS Region in an account.

For example, if for each account that receives the RAM share there are four subnets in the RAM share, then I could share this VPC to a maximum of 5000 ÷ 4 = 1,250 accounts.

But (hypothetically speaking to make the math easy) I had ten vpcs hosted in in that one account, again RAM shared to a an AWS Orgs folder of targeted accounts, and each VPC contained 4 subnets, then each account would receive 10 x 4 = 40 resources in each RAM share. In that case I could share to at most 5000 ÷ 40 = 125 accounts.

Am I looking at this service quota limit correctly?

1 Answer
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5000 is just the default value, and you can increase this limit via the service quotas request in the AWS console. Besides, you calculation looks good if you have multiple subnets within same VPC. Indeed, usually, i will NOT recommend to put too many IP into one subnet, usually, it is just /24 or /22. So, share the subnet with more than 1000 accounts is rare. And it is hard to control. In short, 5000 is just the default value, increase based on your use case and AWS support will help to evaluate the use case for the approval. Hope this help.

AWS
Samuel
answered a year ago

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