@Ansuel It looks like this is the same problem I have described here. More specifically on IPv4 only UDP and ICMP works when the dual stack is configured.
It's possibile that vyatta and LEDE are using the same software with a somewhat broken configuration but it's a bit suspiscious: I think Telecom Italia is at fault here.
Last week I managed to work around it by creating two separate PPPoE interfaces: One with the normal aliceadsl/aliceadsl credentials, IPv4 only with NAT and the other with the IPv6 credential, DHCPv6 prefix delegation and SLAAC. With this setup I have the dual stack properly working.
Can you try this on LEDE and see if it works for you as well?
Right, I'm actually having some routing issue because IPv4 should be completely disabled in the second PPP interface, I'm not sure how to do that though.
i so happy that i find a solution for our problem with tim...
also if you take attention, the ping in ipv4 doesn't get altered by the dual stack ppp (with the ipv6 combo you get 5-10ms more than normal ppp)
I noticed that after 4 hours my laptop with windows 10 loses the default gateway for ipv6.
With wireshark I can see that my pc sends Router Solicitation but LEDE stops sending RAs.
Now the bug has been assigned to the odhcp developer.Could be something ISP related also.
Please vote the task if you have similar issue and comment.
Hopefully we can fix this.