Back in 2021, I checked for IPv6 support in public registries in the Docker Hub IPv6 support thread. Since Docker Hub now has IPv6 support, I wanted to see how other registries have fared.
⚠️ Note: The registry domains referenced here might change in the future. For a full domain list and upto date infomation on IPv6 support, please refer to the v6monitor list.
Results#
Below are the tests I conducted using various registry domains. For each registry, I recorded the Docker endpoint result and used tcpdump to get the auth/blob domain. The registry endpoint is in bold.
Public Container Registries#
Docker Hub: Fully supports IPv6#
- docker.io (registry-1.docker.io): PASS ✅
- docker-images-prod.6aa30f8b08e16409b46e0173d6de2f56.r2.cloudflarestorage.com: PASS ✅
- production.cloudflare.docker.com: PASS ✅
Red Hat Quay: Fully supports IPv6#
- quay.io: PASS ✅
- cdn01.quay.io: PASS ✅
- cdn02.quay.io: PASS ✅
GitHub Container Registry: Only blob endpoint supports IPv6#
- ghcr.io: FAIL ❌
- pkg-containers.githubusercontent.com: PASS ✅
GitLab Container Registry: No IPv6 support#
- registry.gitlab.com: FAIL ❌
- cdn.registry.gitlab-static.net: FAIL ❌
AWS Public ECR: Default endpoint does not have IPv6#
- public.ecr.aws: FAIL ❌
- ecr-public.aws.com: PASS ✅
- d5l0dvt14r5h8.cloudfront.net: PASS ✅
Scaleway Docker Registry: Only blob domain supports IPv6#
- rg.nl-ams.scw.cloud: FAIL ❌
- api.scaleway.com: FAIL ❌
- s3.nl-ams.scw.cloud: PASS ✅
Google Artifact Registry: Fully supports IPv6#
- gcr.io: PASS ✅
Alibaba Cloud Registry: Only auth domain supports IPv6#
- registry.cn-hangzhou.aliyuncs.com: FAIL ❌
- dockerauth.cn-hangzhou.aliyuncs.com: PASS ✅
- aliregistry.oss-cn-hangzhou.aliyuncs.com: FAIL ❌
Public Offical Container Registries#
Microsoft Container Registry: Fully supports IPv6#
- mcr.microsoft.com: PASS ✅
Kubernetes Registry: Supports IPv6#
- registry.k8s.io: PASS ✅
- prod-registry-k8s-io-ap-south-1.s3.dualstack.ap-south-1.amazonaws.com: PASS ✅
⚠️ Note: Blob endpoint seems to use different provider S3 buckets based on regions. For my region, it has IPv6 support. You can find the complete bucket list here.
Redirect Domains#
- registry.access.redhat.com: Domain supports IPv6. Then it redirects to Red Hat Quay.
- lscr.io: Domain does not support IPv6. Then it redirects to GitHub Container Registry.
Summary and Recommendations#
Based on the tests conducted, here’s a summary table of registry IPv6 support and recommendations for environments where IPv6 is crucial:
| Registry | Docker Endpoint | Blob Endpoint | Overall IPv6 Support | Recommendation |
|---|---|---|---|---|
| Docker Hub | ✅ | ✅ | Full | Recommended |
| Red Hat Quay | ✅ | ✅ | Full | Recommended |
| Google Artifact Registry | ✅ | ✅ | Full | Recommended |
| Microsoft Container Registry | ✅ | ✅ | Full | Recommended |
| Kubernetes Registry | ✅ | ✅ | Full | Recommended |
| AWS Public ECR | 🚧 | ✅ | Almost there | Need to use a seperate endpoint |
| GitHub Container Registry | ❌ | ✅ | Partial | Recommend to use with NAT64 |
| Scaleway Docker Registry | ❌ | ✅ | Partial | Recommend to use with NAT64 |
| Alibaba Cloud Registry | ❌ | ❌ | None | Not recommended |
| GitLab Container Registry | ❌ | ❌ | None | Not recommended |
For IPv6-only or IPv6-first environments, I recommend using registries with full IPv6 support such as Docker Hub, Red Hat Quay and Google Artifact Registry.
I recommend using NAT64 because the blob endpoint handles the most bandwidth-intensive downloads, which puts the most burden on the NAT64 server. You can use one from https://nat64.xyz/, but in my testing, most of them seemed to be rate-limited at the Docker endpoint due to high usage.