IPv6 and CDNs: Why Your Website Can Be Up on IPv4 but Down on IPv6

Content Delivery Networks (CDNs) are designed to improve performance and reliability — but when it comes to IPv6, things don’t always work as expected. It’s surprisingly common for a website to be fully available on IPv4 while silently failing for IPv6 users.

1. How CDNs Handle IPv4 and IPv6 Differently

Most CDNs operate separate network stacks for IPv4 and IPv6. Even though they look unified from the outside, internally they may use:

Different edge nodes for IPv4 and IPv6
Separate routing policies
Different firewall or rate-limiting rules

A misconfiguration or partial rollout can easily affect only one protocol — usually IPv6.

2. Common CDN + IPv6 Failure Scenarios

IPv6 enabled in DNS, but not fully enabled at the CDN edge
SSL certificates deployed only on IPv4 listeners
IPv6 traffic blocked by WAF or security rules
Regional IPv6 edge nodes not fully synchronized

In all these cases, IPv4 uptime monitoring shows everything is fine — while real users experience downtime.

3. Why This Downtime Is Hard to Detect

Many businesses test their site from office networks or older ISPs that still default to IPv4. As a result:

The site “works for me”
No alerts are triggered
User complaints seem random or region-specific

This is classic partial downtime — and IPv6 is one of the most common causes.

4. How UptyBots Exposes CDN IPv6 Issues

UptyBots monitors IPv4 and IPv6 independently and from multiple global locations. This makes CDN-related issues immediately visible.

Separate uptime graphs for IPv4 and IPv6
Region-based detection of CDN edge failures
Protocol-specific SSL and response errors
Clear alerts when only IPv6 goes down

5. Best Practices for CDN + IPv6 Reliability

Verify IPv6 is enabled on both DNS and CDN edge nodes
Test SSL termination on IPv6 explicitly
Monitor from multiple regions
Always create separate IPv4 and IPv6 monitors

As IPv6 traffic continues to grow, CDN-related IPv6 issues will only become more visible to users — and more damaging if left undetected.