MT992 and ipv6?

[sarkyscouser]

Has anyone swapped a BT hub with an MT992 modem and managed to get ipv6 working, preferably on g.fast?

I've just replaced my smart hub 2 (which got an ipv6 connection no problem, screenshot below) with an MT992 in front of my Unifi USG.

I can get ipv4 pppoe working no problem but I cannot get an ipv6 address no matter what I try.

In the USG there are 2 ipv6 WAN options, static ipv6 address or DHCPv6 DP.  I've tried requesting a /56 or a /64 PD but no joy.

Output from tcpdump on my USG below.  I'm not having much luck on the Unifi forums as I think this may be a BT specific problem?

tcpdump: listening on pppoe0, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes
11:59:39.662773 IP6 (hlim 1, next-header UDP (17) payload length: 64) fe80::fde8:1b29:524a:2acd.546 > ff02::1:2.547: [udp sum ok] dhcp6 solicit (xid=438d15 (client-ID hwaddr/time type 1 time 662061098 74acb935f2b5) (IA_NA IAID:0 T1:0 T2:0) (rapid-commit) (elapsed-time 0) (option-request DNS-server DNS-search-list))
11:59:39.665831 IP6 (class 0xc0, hlim 255, next-header UDP (17) payload length: 101) fe80::221:5ff:fe70:8434.547 > fe80::fde8:1b29:524a:2acd.546: [udp sum ok] dhcp6 reply (xid=438d15 (server-ID hwaddr type 1 002105708434) (client-ID hwaddr/time type 1 time 662061098 74acb935f2b5) (rapid-commit) (IA_NA IAID:0 T1:0 T2:0 (status-code no addresses)))

For reference this is what my smart hub 2 used to show:

[licquorice]

You definitely need /56PD and DHCP. What settings are available for the LAN side?

[sarkyscouser]

Hi, I tried /56 to begin with but no joy, but also tried /64 as I was a bit confused by the smart hub 2 info.

Lan side I haven't looked at yet as I can't get a GUA on the WAN and the tcpdump responds with "....status-code no addresses". I didn't want to confuse things by moving onto the LAN setup before I've even got the WAN working.

I've tried extra rules in the USG firewall for both DHCPv6 (ports 547 -> 546) and allowing all icmpv6 traffic on both WAN IN and WAN LOCAL but still no joy.

As the MT992 has no interface to tap into how do I know it's not the modem at fault?

[licquorice]

You will only get a link local address on the WAN

Have a look at this thread https://community.bt.com/t5/Home-setup-Wi-Fi-network/IPv6-amp-pfSense-with-BT-FTTP/td-p/2080812

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@sarkyscouser wrote:
As the MT992 has no interface to tap into how do I know it's not the modem at fault?

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Because the modem doesn't deal with the IP layer.

[sarkyscouser]

Here are some screengrabs from the USG for reference:

WAN:

LAN:

[sarkyscouser]

I don't even get a link local address, just an ipv4.
I don't get an fdXX or feXX address on the WAN.
I used to run an opnsense appliance behind the SH2 and a Draytek ADSL router in my ADSL days and figured all this out no problem.
There's something specific about the MT992 / Unifi combo that's not quite right?

[sarkyscouser]

you see, nothing ipv6 related on the WAN (pppoe0/eth0):

[sarkyscouser]

bump

[sarkyscouser · Accepted solution]

OK I have solved this temporarily with the following via ssh into my USG

configure
set interfaces ethernet eth0 pppoe 0 dhcpv6-pd prefix-only
commit
save

I just need to work it into my existing config.gateway.json now to make it permanent...

/56 PD is indeed the right size.