IPv6 not working on iPhones with BE14000 (BT8) Zenwifi system

[Jjack529]

When running an IPv6 test on my iPhones (16 Pro model with latest 18.3 iOS), it fails. However it passes on my desktop and all of our laptops... Has anyone else noticed this or know a fix?

My iPhones show that they have IPv6 addresses when I look at their network information for the wifi, the Router lists their IPv6 Addresses on the network map client list.

I have Xfinity for my provider, with the xfinity modem set to bridge mode.

I have my Zenwifi IPv6 as follows:

Connection type: Native
DHCP-PD: Enable
IPv6 LAN Setting - Auto Configuration Setting: Stateless
Enable Router Advertisement: Enable

I have tried connection type passthrough but that leads to IPv6 not working on any of my devices.

Any thoughts/help would be appreciated!

[jzchen]

I did some searching and all that I gathered is that IPv6 has been around for a while, that it should just work as long as you set the correct settings depending on ISP.  I can't tell you whether it is Apple, ASUS, or both their fault.

You may ask on the ROG forum I think @Saltgrass there has an iPhone 16 Pro (with GT-BE98 Pro) he could probably share his experience...

[Jjack529 · Accepted solution]

So I have finally resolved the issue. I came across a post on another forum from a user with an ASUS router and similar IPv6 instability, and they finally found it to be related to DNS settings - they selected Ad blocking DNS sites in the options, and when they put it back to default/auto (ISP supplied DNS) everything worked... I too had switched to using the cloudflare DNS (1.1.1.1 and 1.0.0.1), and also added DNS servers on the IPv6 page correspondingly (2606:4700:4700::1111 and 2606:4700:4700::1001); I was skeptical that that would be my issue, but sure enough when I switched the DNS settings all back to defaults, my IPv6 test on all my devices now work every time. It wasn't enough to just switch the IPv6 DNS back to default, I had to switch the IPv4 ones back to defaults as well.

Maybe someone can explain why this would break IPv6 on some devices completely and others intermittently failing tests? Is this a bug in the ASUS firmware potentially that is mishandling IPv6 routing when non-default DNS servers are specified? Or is this an ISP issue that is blocking IPv6 traffic that doesn't go through it's DNS servers? Any thoughts would be appreciated!

Thanks!