DX3301-T0 – Missing IPv6 Default Route (Telekom VDSL) / German D0 Firmware Update Request

marksav85

Hello,

I have a German-market Zyxel DX3301-T0 running firmware V5.50(ABVY.2)D0, connected to Deutsche Telekom VDSL using PPPoE with IPv4/IPv6 dual stack.

I'm experiencing an IPv6 connectivity issue and would also like to update the router to the latest compatible firmware.

IPv6 connectivity issue

IPv4 works normally, but IPv6 internet connectivity fails on all devices, both Ethernet and Wi-Fi.

My investigation found the following:

• The router receives global IPv6 WAN addresses and Telekom IPv6 DNS servers.
• IPv6 prefix delegation works, and connected devices receive global IPv6 addresses.
• IPv6 is enabled, including the "Apply as Default Gateway" setting.
• However, the router's IPv6 routing table contains no default route (::/0).
• External IPv6 connections fail, and the router returns "Destination unreachable: No route".
• A router reboot and a Telekom line reset did not resolve the issue.
• The router's own Ping 6 and Trace Route 6 diagnostics also fail to produce successful external IPv6 results. Trace Route 6 returns "can't connect to remote host" for multiple destinations.

This suggests that the router is failing to establish or install the IPv6 default route over the PPPoE connection.

I've attached three screenshots showing the complete routing table. The IPv4 default route (0.0.0.0) is present through ppp1, whereas the IPv6 default route (::/0) is missing.

Firmware update

The router is currently running V5.50(ABVY.2)D0.

I understand that a newer German firmware version, V5.50(ABVY.4)D0, has previously been provided by Zyxel Support.

The official download service offers V5.50(ABVY.7.2)C0, but I cannot establish whether this generic C0 firmware is compatible with my German D0 version.

Unfortunately, the Zyxel support chatbot could not confirm compatibility or provide a support ticket without first installing the generic firmware.

My questions

1. Has anyone experienced this missing IPv6 default route problem on the DX3301-T0, particularly with Deutsche Telekom?
2. Is this a known issue that has been corrected in a newer firmware version?
3. What is the latest compatible German D0 firmware, and where can I obtain it?
4. Can the generic C0 firmware safely replace the German D0 version without affecting VDSL/DSL functionality?
5. Is there a known configuration workaround for the missing IPv6 default route?

I would like to update the firmware for security and maintenance reasons regardless of whether it fixes the IPv6 issue, but I don't want to risk losing my working DSL connection by installing an incompatible firmware variant.

Any advice from Zyxel staff or other DX3301-T0 users would be appreciated.

Category note: My device is a DX3301-T0, not an NBG or ARMOR series router. I selected the Home Router category because I couldn't find a more appropriate category, and the forum interface wouldn't allow me to select another suitable option.

Thank you.

Mark

routing table screen-2.png

routing table screen-1.png

routing table screen-3.png

Peter2

You can switch to the EU firmware instead , it works with german telekom VDSL the EU firmware can be changed to german language too . The Annex B restriction is only with old DSL .

You cant try this firmware to switch from your V5.50(ABVY.2)D0.

https://download.zyxel.com/DX3301-T0/firmware/DX3301-T0_5.50(ABVY.3.1)C0.zip

Here is a rare official source for newest firmware 7.2 :

https://www.zyxel.com/service-provider/emea/en/products/dsl-cpe/vdsl/dx3301dx3300ex3301ex3300-t0-series