Azure Front Door - IPV6 connection issues

Question

Azure Front Door - IPV6 connection issues

Márcio Fornari 6

I Have a front door and a SaaS plataform with many users. When resolving the domain, Azure Front Door returns both IPv4 and IPv6 addresses.

Observed behavior

Users connecting via IPv4 can access the site normally.

Users whose networks prioritize IPv6 experience connection timeouts.

Browsers such as Chrome and Firefox attempt IPv6 first and fail to connect.

Safari falls back to IPv4 more quickly, so it appears to work.

Running tests confirms the issue:

curl -6 https://xxx.com  → connection hangs / 
curl -4 https://xxx.com   → successful response

Affected users must disable IPv6 on their network to access the site successfully.

Additional information

The origin server is healthy and reachable over IPv4.

The issue occurs before traffic reaches the origin.

The Azure Front Door profile does not provide an option to disable IPv6.

Request

We would like Microsoft to:

Investigate IPv6 connectivity to the Azure Front Door edge endpoints resolving for our domain.

Verify whether traffic over IPv6 is being dropped or misrouted.

Confirm if there are regional IPv6 routing issues affecting connectivity.

Advize whether IPv6 can be disabled or adjusted for this endpoint.

Provide best practices to ensure reliable connectivity for IPv6 users.

This issue impacts users whose networks prefer IPv6 and prevents them from accessing our service unless IPv6 is manually disabled.

Venkatesan S 4,735 Reputation points Microsoft External Staff Moderator

2026-02-20T11:59:04.6766667+00:00

Hi Márcio Fornari,

Thank you for contacting us about the Azure Front Door - IPV6 connection issue. We have begun looking into it and will share our suggestions with you as soon as possible. If you have any additional details or concerns in the meantime, please let us know. We appreciate your patience while we work on this.
Márcio Fornari 6 Reputation points

2026-02-20T12:06:42.39+00:00

➜ home curl -6 -I https://xxxx-.azurefd.net

curl: (35) Recv failure: Connection reset by peer

➜ home curl -4 -I https://xxxx-.azurefd.net

HTTP/2 200

date: Fri, 20 Feb 2026 12:30:32 GMT

content-type: text/html

content-length: 638

last-modified: Thu, 19 Feb 2026 19:54:32 GMT

vary: Accept-Encoding

etag: "69976a78-27e"

x-azure-ref: 20260220T123032Z-1854948875fk7l52hC1CPQfhp80000001myg000000004up1

x-cache: CONFIG_NOCACHE

accept-ranges: bytes

the test confirms that front door not accept IPV6
Venkatesan S 4,735 Reputation points Microsoft External Staff Moderator

2026-02-20T12:47:39.7333333+00:00
Hi Márcio Fornari,

Thanks for reaching out in Microsoft Q&A forum,

Confirm if there are regional IPv6 routing issues affecting connectivity.

Azure Front Door resolves both IPv4 and IPv6 addresses for your domain, letting IPv4 users connect smoothly while IPv6-preferring networks (like those used by Chrome and Firefox) hit timeouts before traffic even reaches your origin. Safari works better due to quicker IPv4 fallback. This drops at the Front Door edge, not your healthy backend, and there's no simple toggle to shut off IPv6.

Your setup runs Client > Azure Front Door > Load Balancer > Nginx origin servers, where the IPv6 failure happens upfront at Front Door's edge nodes advertising AAAA records, despite the Load Balancer and Nginx handling IPv4 just fine.

Browsers follow Happy Eyeballs, trying IPv6 first and stalling if Front Door mishandles or drops those packets common in reports, especially with IPv4-only backends like your Load Balancer.

DNS Trick: Edit your DNS provider to drop AAAA (IPv6) records, serving only A (IPv4)—forces all clients to IPv4. Verify with dig AAAA yourdomain.com showing empty.

Test Edge: curl -6 -v https://yourdomain.com or directly to Front Door endpoint (https://yourfd.azurefd.net) for handshake clues.

Troubleshoot below steps:

Portal: Front Door Metrics > Filter IPv6 connection failures; check backend health probes (IPv4-only).

Logs: Enable to Log Analytics, query clientIP startswith "::" for IPv6 drops.

Load Balancer: Confirm no IPv6 inbound; Nginx logs will lack IPv6 hits, proving upstream issue.

Set alerts on IPv6 failures via Azure Monitor. Long-term, enable dual stack on Load Balancer/Nginx if viable. User notice: Suggest IPv6 disable as temp fix. Use Front Door rules to detect/redirect IPv6 if advanced.

Reference:

https://learn.microsoft.com/en-us/azure/virtual-network/ip-services/ipv6-overview

Kindly let us know if the above helps or you need further assistance on this issue.

Please “up-vote” wherever the information provided helps you, this can be beneficial to other community members.
Venkatesan S 4,735 Reputation points Microsoft External Staff Moderator

2026-02-23T04:09:18.61+00:00

Hi Márcio Fornari,

We haven't heard back from you regarding our last response and wanted to check if you had the opportunity to review our previous post.

Please "up vote" if the information helped you. This will help us and others in the community as well
Márcio Fornari 6 Reputation points

2026-02-23T11:34:44.8066667+00:00

The connection doesn’t seem to even reach the front door, so I’m not sure if there is some kind of blocking in place. At this point, I can’t think of any other alternatives — I’ve already tried everything I could.

This forum doesn’t seem to be the appropriate channel for this type of support. I would like to get in direct contact with a Microsoft technician to help resolve this issue.
Vallepu Venkateswarlu 6,045 Reputation points Microsoft External Staff Moderator

2026-02-23T17:18:49.9066667+00:00

Hi @ Márcio Fornari,

Could you please share the requested details in a private message so we can troubleshoot further?
Praveen Bandaru 10,720 Reputation points Microsoft External Staff Moderator

2026-02-26T13:56:21.2833333+00:00

Hello Márcio Fornari
I just wanted to follow up and see if you had a chance to review my answer to your question. Please let us know if you found it useful, and don't hesitate to contact us if you have any further questions.

I hope the above answer helps you! Please let us know if you have any further questions.

Please don't forget to "upvote" where the information provided will help you, this can be beneficial to other members of the community.
Praveen Bandaru 10,720 Reputation points Microsoft External Staff Moderator

2026-02-27T11:09:58.0566667+00:00

Hello Márcio Fornari

I just wanted to follow up and see if you had a chance to review my answer to your question. Please let us know if you found it useful, and don't hesitate to contact us if you have any further questions.

I hope the above answer helps you! Please let us know if you have any further questions.

Please don't forget to "upvote" where the information provided will help you, this can be beneficial to other members of the community.

1 answer

Your answer

Venkatesan S 4,735 Reputation points Microsoft External Staff Moderator

2026-02-20T11:59:04.6766667+00:00

Hi Márcio Fornari,

Thank you for contacting us about the Azure Front Door - IPV6 connection issue. We have begun looking into it and will share our suggestions with you as soon as possible. If you have any additional details or concerns in the meantime, please let us know. We appreciate your patience while we work on this.
Márcio Fornari 6 Reputation points

2026-02-20T12:06:42.39+00:00

➜ home curl -6 -I https://xxxx-.azurefd.net

curl: (35) Recv failure: Connection reset by peer

➜ home curl -4 -I https://xxxx-.azurefd.net

HTTP/2 200

date: Fri, 20 Feb 2026 12:30:32 GMT

content-type: text/html

content-length: 638

last-modified: Thu, 19 Feb 2026 19:54:32 GMT

vary: Accept-Encoding

etag: "69976a78-27e"

x-azure-ref: 20260220T123032Z-1854948875fk7l52hC1CPQfhp80000001myg000000004up1

x-cache: CONFIG_NOCACHE

accept-ranges: bytes

the test confirms that front door not accept IPV6
Venkatesan S 4,735 Reputation points Microsoft External Staff Moderator

2026-02-23T04:09:18.61+00:00

Hi Márcio Fornari,

We haven't heard back from you regarding our last response and wanted to check if you had the opportunity to review our previous post.

Please "up vote" if the information helped you. This will help us and others in the community as well
Márcio Fornari 6 Reputation points

2026-02-23T11:34:44.8066667+00:00

The connection doesn’t seem to even reach the front door, so I’m not sure if there is some kind of blocking in place. At this point, I can’t think of any other alternatives — I’ve already tried everything I could.

This forum doesn’t seem to be the appropriate channel for this type of support. I would like to get in direct contact with a Microsoft technician to help resolve this issue.
Vallepu Venkateswarlu 6,045 Reputation points Microsoft External Staff Moderator

2026-02-23T17:18:49.9066667+00:00

Hi @ Márcio Fornari,

Could you please share the requested details in a private message so we can troubleshoot further?
Praveen Bandaru 10,720 Reputation points Microsoft External Staff Moderator

2026-02-26T13:56:21.2833333+00:00

Hello Márcio Fornari
I just wanted to follow up and see if you had a chance to review my answer to your question. Please let us know if you found it useful, and don't hesitate to contact us if you have any further questions.

I hope the above answer helps you! Please let us know if you have any further questions.

Please don't forget to "upvote" where the information provided will help you, this can be beneficial to other members of the community.
Praveen Bandaru 10,720 Reputation points Microsoft External Staff Moderator

2026-02-27T11:09:58.0566667+00:00

Hello Márcio Fornari

I just wanted to follow up and see if you had a chance to review my answer to your question. Please let us know if you found it useful, and don't hesitate to contact us if you have any further questions.

I hope the above answer helps you! Please let us know if you have any further questions.

Please don't forget to "upvote" where the information provided will help you, this can be beneficial to other members of the community.

Answer 1

Hello **Márcio Fornari
**This behavior is expected if IPv6 is being coming and your backend does not support IPv6, as name resolution will fail.

Also, with dynamic IP allocation at the front door, the IP address changes each time, making it impossible to set up a static allow list.

Please validate both the working and non-working HAR files and analyze where the failure happens. Share both HAR files with us through a private message.

If possible, collect the tracking reference ID from the front door access logs for further investigation. You can also find the X-Azure reference ID in the HAR file.

Please check your activity logs to verify whether the request is reaching your front door backend when the issue occurs and also confirm how the backend is responding to your front door.

You may collect the tracking reference ID from the access logs when the issue occurs and uses it to review logs in your Azure portal. For instructions on collecting logs, refer to the following document:

https://learn.microsoft.com/en-us/azure/frontdoor/refstring?source=recommendations&tabs=edge

I hope the above answer helps you! Please let us know if you have any further questions.

Please don't forget to "upvote" where the information provided will help you, this can be beneficial to other members of the community.

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Azure Front Door - IPV6 connection issues

Observed behavior

Additional information

Request

1 answer

Your answer