Not receiving IPv6 address in PPPoE tunnel

[wvthoognl]

Hi everyone,

I've been struggling to get an IPv6 address from my ISP (KPN in The Netherlands). Despite following several tutorials on how to set this up, I haven't been able to receive an IPv6 address over the PPPoE tunnel interface. However, I can successfully obtain an IPv4 address on the same interface.

Here are the tutorials I used as guides:

• KPN Community Forum - FortiGate 60F Setup
• Network Dynamics - IPv6 Setup

My Setup

• Router: FortiGate 60F (7.2.10)
• Switch: FortiSwitch 108F-FPOE (connected via FortiLink)
• Access Points: Two FortiAP 231F
• WAN Interfaces:
  • WAN1 (connected to KPN ISP)
  • WAN2 (connected to a second ISP)
• Both WAN1 and WAN2 are configured as members of an SD-WAN zone.

Current Configuration

For simplicity, I’ve removed WAN1 from the SD-WAN zone for testing. This ensures SD-WAN settings don’t interfere with IPv6 troubleshooting.

Physical Interface (WAN1):

config system interface
    edit "wan1"
        set vdom "root"
        set type physical
        set snmp-index 1
        set mtu-override enable
        set mtu 1514
    next
end

VLAN on WAN1:

config system interface
    edit "KPN-VLAN6"
        set vdom "root"
        set allowaccess ping
        set estimated-upstream-bandwidth 100000
        set estimated-downstream-bandwidth 100000
        set snmp-index 27
        set interface "wan1"
        set mtu-override enable
        set mtu 1506
        set vlanid 6
    next
end

PPPoE Tunnel on VLAN:

config system interface
    edit "KPN-PPPOE"
        set vdom "root"
        set mode pppoe
        set allowaccess ping
        set type tunnel
        set estimated-upstream-bandwidth 100000
        set estimated-downstream-bandwidth 100000
        set role wan
        set snmp-index 34
        config ipv6
            set ip6-mode dhcp
            set ip6-allowaccess ping
            set dhcp6-prefix-delegation enable
            config dhcp6-iapd-list
                edit 1
                    set prefix-hint 2a02:a45f:xxyy::/48
                next
            end
        end
        set dns-server-override disable
        set interface "KPN-VLAN6"
    next
end

PPPoE Settings:

config system pppoe-interface
    edit "KPN-PPPOE"
        set ipv6 enable
        set device "KPN-VLAN6"
        set username "internet"
        set password ENC 1lYRTvns9DlUt/PU7NbygLmBxmOmqPSI5aXdgHhhiVA4WUkSx46gsH49365bf7fn0AcH562j5mC21JC6wsMteDAi0/xZXtSwkgse9gal18veiCzQiQ0t1JJLI+kzDO8gzVV1yQLhUiFHnhG1Ll2TcHUCWqCsdZ7aq8i8Hs9JJfxV+a6M4dY0EtptLcgTE723fMRGOw==
    next
end

The PPPoE tunnel refuses to retrieve an IPv6 address from the ISP. To debug, I ran:

diagnose debug application dhcp6c -1
diagnose debug enable

This generated many repetitive messages, but no SOLICIT requests were observed

WVH-FW-01 # [debug]dhcp6_check_timer() called
[info]client6_mainloop() timeout=10 sec, cfd=5, kfd=6
[debug]dhcp6_check_timer() called
[info]client6_mainloop() timeout=10 sec, cfd=5, kfd=6
[debug]dhcp6_check_timer() called
[info]client6_mainloop() timeout=10 sec, cfd=5, kfd=6
[debug]dhcp6_check_timer() called
[info]client6_mainloop() timeout=8 sec, cfd=5, kfd=6
[debug]dhcp6_check_timer() called

I also tried monitoring for DHCPv6 requests with:

WVH-FW-01 # diagnose sniffer packet KPN-PPPOE "udp port 546 or udp port 547" 6
interfaces=[KPN-PPPOE]
filters=[udp port 546 or udp port 547]

However, it appears no DHCPv6 requests are being sent.

In a desperate attempt, I connected the ISP-provided router directly. It worked immediately, obtaining both IPv4 and IPv6 addresses without any issues.

Clearly, I’m missing a configuration option somewhere. Has anyone experienced this specific issue or successfully configured IPv6 with KPN as their ISP? Any suggestions or advice would be greatly appreciated.

Looking forward to your insights. Thanks for your time!

[Anthony_E]

Hello,

Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible.

Thanks,

[wvthoognl]

Thank you Anthony, looking forward to your suggestions

[Secusaurus]

Hi @wvthoognl,

We are also having issues with the correct deployment of IPv6 with our ISP (Deutsche Telekom), but I think, we are one step ahead of your setup.

Please note that you posted your ISP-password above. In case you can edit your post, you should remove it from your output.

We defined pppoe directly on the vlan interface (which must be id 7 for our ISP), so the setup looks like that:

    edit "VLAN-7"
        set vdom "WAN"
        set mode pppoe
        set allowaccess ping
        set role wan
        config ipv6
            set ip6-mode pppoe
            set ip6-allowaccess ping
            set dhcp6-prefix-delegation enable
            set autoconf enable
            config dhcp6-iapd-list
                edit 1
                    set prefix-hint ::/56
                next
            end
        end
        set username ...
        set password ...
        set interface "port2"
        set vlanid 7
    next

We do receive an IPv6 address here, but not a prefix list, which I could then hand over to the sub-networks behind. This is the issue I am currently investigating in our setup. But perhaps you can get one step further with that input.

Best,

Christian