From e0aba748c5313310f5e4b5c13e12dfcec0085289 Mon Sep 17 00:00:00 2001 From: Sean Killeen Date: Tue, 30 Sep 2025 15:51:09 -0400 Subject: [PATCH 1/3] =?UTF-8?q?Create=20Blog=20=E2=80=9C2025-09-30-field-n?= =?UTF-8?q?otes-solved-docker-pull-from-mcr-microsoft-com-failing=E2=80=9D?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...ker-pull-from-mcr-microsoft-com-failing.md | 42 +++++++++++++++++++ 1 file changed, 42 insertions(+) create mode 100644 _posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md diff --git a/_posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md b/_posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md new file mode 100644 index 00000000..080adafe --- /dev/null +++ b/_posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md @@ -0,0 +1,42 @@ +--- +title: "[Field Notes] Solved: docker pull from mcr.microsoft.com failing" +comments: true +tags: + - field-notes + - dns + - docker + - verizon +date: 2025-09-30 15:51 -0400 +--- +## Background + +Recently had an issue where some of our developers couldn't pull Docker images from `mcr.microsoft.com`. This happened over time, and sometimes when they changed locations. + +## Troubleshooting + +Finally narrowed it down to those using Verizon, using Verizon DNS, on IPv6. + +| ISP | IPv6 Enabled | Machine DNS | Docker DNS | Result | +| ----| -------------| --- | ---------- | -------| +| Comcast | Any | Any | Any | ✅ | +| Verizon | False | Verizon Default | Default | ✅ | +| Verizon | True | 1.1.1.1 | Default | ✅ | +| Verizon | True | Verizon Default | 1.1.1.1 | ✅ | +| Verizon | True | Verizon Default | Default | ❌ | + +## How to Fix + +As far as I can tell, there are a few ways to resolve this issue. + +* You can move off of Verizon 😉 +* You can disable IPv6 on your machine, allowing only IPv4. However, this seems a little drastic +* You can set your machine's DNS server away from Verizon's DNS to something like CloudFlare's `1.1.1.1` or similar. +* You can update the Docker Engine settings in Docker for Windows to add `"dns": ["1.1.1.1"]` to the top-level JSON. This + +## Final Thoughts + +Still not sure why this is happening, or why it seems to be happening only in this specific scenario. DNS isn't my strong suit, but I hope someone smarter than me comes along and adds more information here. + +For now, just happy to be able to unblock my team. + +Happy coding! From a95f092a457ae76cbd7529f1f3b68d708551fb8d Mon Sep 17 00:00:00 2001 From: Sean Killeen Date: Tue, 30 Sep 2025 15:51:51 -0400 Subject: [PATCH 2/3] =?UTF-8?q?Update=20Blog=20=E2=80=9C2025-09-30-field-n?= =?UTF-8?q?otes-solved-docker-pull-from-mcr-microsoft-com-failing=E2=80=9D?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...d-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/_posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md b/_posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md index 080adafe..d305dd7e 100644 --- a/_posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md +++ b/_posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md @@ -31,7 +31,7 @@ As far as I can tell, there are a few ways to resolve this issue. * You can move off of Verizon 😉 * You can disable IPv6 on your machine, allowing only IPv4. However, this seems a little drastic * You can set your machine's DNS server away from Verizon's DNS to something like CloudFlare's `1.1.1.1` or similar. -* You can update the Docker Engine settings in Docker for Windows to add `"dns": ["1.1.1.1"]` to the top-level JSON. This +* You can update the Docker Engine settings in Docker for Windows to add `"dns": ["1.1.1.1"]` to the top-level JSON. This will change the DNS settings only within docker, so pulling images should work once more without any changes affecting your wider machine. ## Final Thoughts From 6a29b467768d792801d42d922a2a9cdef760008d Mon Sep 17 00:00:00 2001 From: Sean Killeen Date: Tue, 30 Sep 2025 15:52:03 -0400 Subject: [PATCH 3/3] =?UTF-8?q?Update=20Blog=20=E2=80=9C2025-09-30-field-n?= =?UTF-8?q?otes-solved-docker-pull-from-mcr-microsoft-com-failing=E2=80=9D?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...d-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/_posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md b/_posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md index d305dd7e..877d231f 100644 --- a/_posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md +++ b/_posts/2025-09-30-field-notes-solved-docker-pull-from-mcr-microsoft-com-failing.md @@ -30,7 +30,7 @@ As far as I can tell, there are a few ways to resolve this issue. * You can move off of Verizon 😉 * You can disable IPv6 on your machine, allowing only IPv4. However, this seems a little drastic -* You can set your machine's DNS server away from Verizon's DNS to something like CloudFlare's `1.1.1.1` or similar. +* You can set your machine's DNS server away from Verizon's DNS to something like Cloudflare's `1.1.1.1` or similar. * You can update the Docker Engine settings in Docker for Windows to add `"dns": ["1.1.1.1"]` to the top-level JSON. This will change the DNS settings only within docker, so pulling images should work once more without any changes affecting your wider machine. ## Final Thoughts