Recently bought two Eve devices: one outlet, one plug. I cannot for the life of me get these to join and the continue to work unless HA is on the same IP network as where my phone is connected when adding them. Android phone connected to IOT network > HA Companion App > settings > Devices & services > Devices > Add Device > Matter > No, it’s new > scan or type in code > NEVER JOINS. If I move the HA to the IOT network things connect pretty quickly like you would expect. If I leave HA there everything works fine. If I move HA back to the main VLAN, matter devices become unavailable. Everything I have ever seen says to keep HA off the IOT network. So, am I right to understand that if I want to use the HA Matter over thread and the OTBR I have to leave HA on the IOT network? Has anyone gotten this to work with them on separate networks? I have read about an mDNS reflector, but I was under the impression that my UDM was already passing that between networks. Any help or reassurance that my findings are correct would be appreciated. Thanks!
HA OS installed on NUC:
Core - 2025.4.4
Supervisor - 2025.04.1
Operating System - 15.2
Frontend - 20250411.0
SkyConnect - Thread Only
Matter/Thread/OTBR integrations installed
Network Gear Unifi:
“Main” VLAN (5 & 6 GHz)- HA lives here
“IOT” VLAN (2.4 only) - All things IOT live here
mDNS enabled on both
ULA IPv6 enabled on both
Firewall rules allow all traffic everywhere (internally) as part of testing
For fun, firewall rules that allow 8123,5353,5683,1900,1883,8081 from HA to IOT & return traffic allowed
The problem is that most mDNS reflectors don’t seem to work correctly with IPv6 (i.e. snoop and masquerade all the mandatory non-routable fe80 LLAs, which are still present alongside any ULAs configured and may still appear in mDNS announcements), so the combination of Matter requiring both makes it especially hard to use with separate vlans.
Instead of fighting with complex reflector and firewall configs, I have chosen instead to put a second (tagged) interface of my HA server on my IoT vlan and Matter works fine. If you do get your reflector working though, please let us know what settings work for you.
The short answer is matter over thread (MoT) is still the new kid on the block, in active development and not currently working in any stable way with network segmention. It’s likely not a compatible item with design of it people just want to be able to plug it in and have it work, be secure etc. So Ideally should never need it, i couldnt find it on any roadmap anyway.
So as a few have suggested if you want it working and stable right now you have to expose your border router (HA controller in your case), the device you use to add matter devices and the matter IoT devices themselves directly to each other on the same network vlan and its suggest the same 2.4ghz. Flat consumer / home networks may have less matter thread issues.
I reallyreally do like where the standard is going though.