Two IPv6 prefixes behind fibre ONT Huawei HG8245Q2

[ipv6subnethuawei]

Hi,

I am with the Austrian ISP Energie AG on a fibre connection.
I am running their ONT Huawei HG8245Q2 and behind it a S920 with OpenWRT.

The S920 which acts as the router for the home network uses two networks (LAN and guest).

I am now trying to get IPv6 connectivity working on both networks.
Sadly, the S920 OpenWRT router on the WAN interface only receives a /64 prefix.

Here are screenshots from the ONT settings, which seem to suggest that the ONT receives a /56 prefix:

Any ideas welcome.

[ipv6subnethuawei]

[ipv6subnethuawei]

[eduperez]

Just to be sure: your ONT is also acting as a router, right?

[mk24]

Do you have reqprefix configured on the wan interface in OpenWrt? The upstream may require requesting a specific prefix. Try different values between 56 and 63. 56 and 60 would be ones to try first.

[ipv6subnethuawei]

Thank you for your quick replies and willingness to help! Sorry for not being as precise as possible in the beginning.

@eduperez

Just to be sure: your ONT is also acting as a router, right?

Yes, that is correct. I have not found a way to put the ONT into bridge mode, sadly.

@mk24

Do you have reqprefix configured on the wan interface in OpenWrt? The upstream may require requesting a specific prefix. Try different values between 56 and 63. 56 and 60 would be ones to try first.

I have deleted and recreated the wan6 interface to make sure I am on default settings. Next I tried all Request IPv6-prefix of length settings between 63 and 56. All of them result in IPv6-PD: of the same /64 prefix for the wan6 interface. One of the "child" interfaces (guest and lan) snatches that prefix, and the other "child" interface stays without IPv6.

[eduperez]

Are there any IPv6 options on the LAN on the ONT?

[spot0]

That's a sad situation as you received a /56 from your ISP. Have you tried this solution for AT&T? https://openwrt.org/docs/guide-user/network/wan/isp-configurations

[alexq]

@ipv6subnethuawei

on the WAN interface only receives a /64 prefix.

@ipv6subnethuawei , similar situation was resolved by requesting and obtaining multiple /64 blocks on the WAN after the ISP Huawei fiber router. Please review the information and try it:

@alexq

ISP uses the same IPv6 /64 prefix delegation method as AT&T does.

See my test results:

So, I was able to get 4 different IPv6-PD /64 delegated prefixes (didn't try more):

IPv6-PD: 2a01:xxxx:xxxx:2503::/64
IPv6-PD: 2a01:xxxx:xxxx:2504::/64
IPv6-PD: 2a01:xxxx:xxxx:2505::/64
IPv6-PD: 2a01:xxxx:xxxx:2506::/64