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okapi
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09/28/2026 8:32 PM

Intermittent IPv6 TLS connection resets to specific Microsoft Azure ranges — confirmed not a router/device issue

I'm seeing consistent TLS handshake resets (10–50% failure rate) over IPv6 to several Microsoft/Azure destinations, while IPv4 to the same hosts is 100% reliable and IPv6 to dozens of other providers (Google, Cloudflare, Meta, Wikipedia, Amazon, Akamai) is also 100% reliable on the same connection.

Affected IPv6 destinations:

  • 2603:1030:a0b::10 (management.azure.com)
  • 2603:1061:10:1::16 (dev.azure.com)
  • 2603:1061:11::21 (portal.azure.com)

Evidence:

  • Repeated curl tests over 3+ days from my home connection show 10–50% success to these addresses; the same test from a T-Mobile hotspot to the identical addresses is 100% successful.
  • A wider test of 19 popular sites shows only Microsoft/Azure destinations failing over IPv6 at home; every other provider is 100%.
  • Traceroute shows the path leaving Comcast's network around be-4213-pe13.ashburn.va.ibone.comcast.net before reaching Microsoft's network.
  • This looks like a routing/peering issue between Comcast and Microsoft's network for these specific IPv6 ranges, not a problem with my equipment (UniFi gateway ruled out — the same gateway handles every other IPv6 destination at 100%).

Can this be escalated to network engineering for review of IPv6 peering/routing to Microsoft's 2603:1030::/32 and 2603:1061::/32 ranges? Happy to provide full logs.

Separately, I'm also seeing intermittent IPv6 TLS resets to Netflix (2a00:86c0:2043::1) from home, though I haven't isolated that one as cleanly.

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1 hour ago

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XfinityDilary

Official Employee

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3.8K Messages

1 hour ago

okapi. Thank you for providing such detailed testing and documentation. I appreciate the time you've put into isolating the issue. Based on the information you've shared, I can see why you're concerned, particularly since you've observed different behavior between IPv4 and IPv6 and have reproduced the results over multiple days. However, we're unable to determine from these test results alone whether the issue is being caused by a routing, peering, or network infrastructure problem. We'd be happy to take a closer look and review the connection, signal history, and any available network diagnostics for your location. Could you please send our team a Direct Message with your name and service address? Our team can take a further look at this issue.

 

To send a Direct Message:

Click "Sign In" if necessary

• Click the "Direct Messaging chat" icon

• Click the "New message" (pencil and paper) icon

• Type "Xfinity Support" in the "To:" line and select "Xfinity Support" from the drop-down list that appears. The "Xfinity Support" graphic replaces the "To:" line

• Type your message in the text area near the bottom of the window

• Press Enter to send it

 

For an example of how to send us a direct message, check out this link:

https://forums.xfinity.com/conversations/guidelines/how-to-direct-messaging-within-the-forum/697ba1e570934d009185c514

 

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EG

Expert

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121.7K Messages

1 hour ago

@okapi @XfinityDilary 

Please circle back here and post any possible solutions for the issue here in these open public forums so that all readers here may benefit from the exchange / info. This is in keeping with the spirit for which these public help forums were originally intended. Thank you.

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