Today I am happy to announce that objects in Amazon S3 buckets are now accessible via IPv6 addresses via new “dual-stack” endpoints. When a DNS lookup is performed on an endpoint of this type, it returns an “A” record with an IPv4 address and an “AAAA” record with an IPv6 address. In most cases the network stack in the client environment will automatically prefer the AAAA record and make a connection using the IPv6 address.
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S3 Feature Support – IPv6 support is available for all S3 features with the exception of Website Hosting, S3 Transfer Acceleration, and access via BitTorrent.
Source: Now Available – IPv6 Support for Amazon S3 | AWS Blog
This is important since it becomes likely that with IPv6 support each S3 bucket could get its very own address and not need to rely on a combo of DNS and NAT for net access.