The access restriction must be applied to the REST API, not merely to the static website bucket. API Gateway resource policies can control who can invoke an API and can restrict access by source IP address ranges or CIDR blocks. That directly satisfies the requirement that only computers from the corporate CIDR range can invoke the API. An S3 bucket policy would restrict access to the static website content, but the API endpoint could still be called directly unless API Gateway is also protected. An IAM service- linked role is not the correct control plane for client source IP filtering. Network ACLs apply at the subnet level inside a VPC and do not control public API Gateway invocation. AWS documentation confirms API Gateway resource policies support specified source IP address ranges. ( AWS Documentation )

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