ONT cannot get IPV6 with PPPoE

The ONT is not receiving the IPv6 address by PPPoE, the BRAS assigns prefix and address through a DHCPv6 server. The ONT only gets the prefix, but not the address.

The ONT can get some debuggings and found that PPP establishment is successful, but the ONT is sending a LCP ProtRej (Protocol Reject) so is suspected the ONT is not accepting the IPv6 address

1. Verified the WAN Configuration and is needed the IPv6 and prefix be obtained by DHCPv6.

2. We can make the debuggings logging by CLI to the ONT and apply the following command

3. Also took some packet captures with the command set ethportmirror sourceport X destport Y mirrordate 2 enable 1 

4. Checking the packet capture, the Protocol Reject packet is because the BRAS is sending a PPP IPCP Configuration request, but the ONT will reject the IPCP packet, only will accept IPv6CP Configuration Request

5. In the packet captures we can see that the ONT requests the IPv6 address and prefix of the WAN through DHCPv6, but the BRAS only allocates the prefix information and does not allocate the IPv6 address. 

  a) The ONT requested the IPv6 address (IA_NA) and IPv6 prefix information (IAPD) in the DHCPv6 Solicit message:

6. Checkin the response, the BRAS only replies the IPv6 prefix information (IAPD) in the Advertise message, and does not reply the IPv6 address information (IA_NA), so ONT's WAN cannot obtain an IPv6 address. Need to further investigate the problem of the upper BRAS。

Although the ONT is requesting the IPv6 address in the IA_NA packet and the prefix in the IAPD, the ONT is only receiving the IAPD.

7. The Neighbor Discovery protocol uses a Router Solicitation and Router Advertisement to get the peer IPv6 address.

We checked that the ONT WAN interface sends RS (Router Solicitation) messages, but the ONT has not received the RA (Router Advertisement) message from the BRAS. Therefore, it is also necessary to confirm if the BRAS supports the Neighbor Discovery Protocol

The BRAS is not sending the IPv6 address because it does not have the neighbor discovery protocol enabled.

Enable the Neighbor Discovery Protocol in the BRAS.