Not receiving IPv6 address in PPPoE tunnel

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!