topic Re: Possible MAP-T issue? in Broadband

Possible MAP-T issue?

FibreFodder — Thu, 13 Aug 2026 14:45:04 GMT

Current setup, stopped working today:

Service: FTTP (900/100).

Router: Ubiquiti UDM-SE.

Config: No DHCP option 61 + IPv6 disabled. When I moved to Sky (30 July 2026), this setup worked, no tinkering required.

Line health: Very good until a few days ago, noted 5-8% packet loss. Earlier today the connection dropped and now the UDM-SE cannot connect.

ONT: Power and PON are solid green, no LAN activity.

Fault diagnosis, so far:

Powered off the ONT for 10+ mins.
Performed a factory reset of the ONT.
Restarted the UDM-SE.
Plugged in the Sky Hub Max 6 and it connects, Power/PON/LAN all green on ONT.
On the Sky Hub I noticed the WAN connection is set to MAP-T (1:8 I think).

Any suggestions on how to fix/fault find are most welcome!

TIA

Re: Possible MAP-T issue?

TimmyBGood — Thu, 13 Aug 2026 14:56:00 GMT

@FibreFodder

Has there been a Ubiquiti update?

They do love to break things....

Re: Possible MAP-T issue?

FibreFodder — Thu, 13 Aug 2026 14:59:47 GMT

I know what you mean! 😉

(UDM-SE) Autoupdate is disabled and I usually wait a few weeks before applying updates. I haven't done one in a couple of weeks.

Re: Possible MAP-T issue?

Chrisee — Thu, 13 Aug 2026 15:02:16 GMT

@FibreFodder for a router to be offered a MAP-T connection it must advertise support for DHCPv6 Option95 which the Sky Maxhub does. Ubquiti, bless them, managed to advertise that support but forgot to actually program their routers correctly. This started roughly 10 years ago but was finally fixed in a firmware release around two years ago so unless you have flashed so early firmware this should not be an issue.

I would check that you have correctly set the Ubquiti unit to use DHCPv6 PD with IP6 enabled. Thst set up is supported by all but 20% of Sky's Openreach connections. If you are unlucky you will require to use DHCPv4 Option 61.

Re: Possible MAP-T issue?

FibreFodder — Thu, 13 Aug 2026 15:11:47 GMT

@TimmyBGood , @Chrisee , Thank you both for the replies.

I'll try DHCP option 61. Although the connection has worked without it until today. I'll report back with the results.

Re: Possible MAP-T issue?

FibreFodder — Thu, 13 Aug 2026 15:53:56 GMT

Config

VLAN ID: Unchecked (disabled).

MAC Address Clone: Unchecked

Smart Queues: Unchecked

IGMP Proxy: Unchecked

UPnP: Unchecked

IPv4 Config

DHCP: Enabled

DHCP Client Option: 61

DHCP Client Option value: anything@skydsl|password

Auto DNS Server: Enabled

IPv6 Config

DHCPv6: Enabled

Prefix Designation Size (PD): 56 (auto box unchecked).

ONT Power cycled.

Same result, no connection.

Re: Possible MAP-T issue?

FibreFodder — Thu, 13 Aug 2026 18:02:50 GMT

Often, it’s something simple not fandango complicated … faulty network cable between the ONT and router. 😂

Thank you to the folks who replied.