Unable to set up ZBT-2 with Zigbee2MQTT and Mosquitto broker

Hi, I am trying to add a Zigbee network to my HA setup (never had Zigbee before and nothing Zigbee-related previously installed).

Installation method Home Assistant OS on RPi4
Core 2025.11.3
Supervisor 2025.11.5
Operating System 16.3
Frontend 20251105.1

I bought the new coordinator ZBT-2, went through the setup procedure using the right choices for setting it up with Zigbee2MQTT and MQTT and flashed the firmware. The device appears in the list of devices and today the firmware was updated to EmberZNet Zigbee 7.4.4.6.

I then added the MQTT broker and set it up with username “smarthome” and pw “smarthome”.
I then installed the add-on Zigbee2MQTT and in the MQTT section configured the same username and pw, server: mqtt://core-mosquitto:1883, base_topic: zigbee2mqtt. Serial: adapter: ember, baud rate: 460800, rtscts: enabled. port: set up by id.

HERE IS THE PROBLEM:

Z2M (ver. 2.6.3-1) refuses to start.

log:

[16:01:48] INFO: Preparing to start…
[16:01:48] INFO: Socat not enabled
[16:01:50] INFO: Starting Zigbee2MQTT…
Starting Zigbee2MQTT without watchdog.
[2025-11-28 16:01:55] info: z2m: Logging to console, file (filename: log.log)
[2025-11-28 16:01:55] info: z2m: Starting Zigbee2MQTT version 2.6.3 (commit #unknown)
[2025-11-28 16:01:55] info: z2m: Starting zigbee-herdsman (6.3.2)
[2025-11-28 16:01:55] info: zh:ember: Using default stack config.
[2025-11-28 16:01:55] info: zh:ember: ======== Ember Adapter Starting ========
[2025-11-28 16:01:55] info: zh:ember:ezsp: ======== EZSP starting ========
[2025-11-28 16:01:55] info: zh:ember:uart:ash: ======== ASH Adapter reset ========
[2025-11-28 16:01:55] info: zh:ember:uart:ash: Serial port opened
[2025-11-28 16:01:55] info: zh:ember:uart:ash: ======== ASH starting ========
[2025-11-28 16:02:00] info: zh:ember:uart:ash: ======== ASH Adapter reset ========
[2025-11-28 16:02:00] info: zh:ember:uart:ash: ======== ASH starting ========
[2025-11-28 16:02:05] info: zh:ember:uart:ash: ======== ASH Adapter reset ========
[2025-11-28 16:02:05] info: zh:ember:uart:ash: ======== ASH starting ========
[2025-11-28 16:02:10] info: zh:ember:uart:ash: ======== ASH Adapter reset ========
[2025-11-28 16:02:10] info: zh:ember:uart:ash: ======== ASH starting ========
[2025-11-28 16:02:16] info: zh:ember:uart:ash: ======== ASH Adapter reset ========
[2025-11-28 16:02:16] info: zh:ember:uart:ash: ======== ASH starting ========
[2025-11-28 16:02:21] error: z2m: Error while starting zigbee-herdsman
[2025-11-28 16:02:21] error: z2m: Failed to start zigbee-herdsman
[2025-11-28 16:02:21] error: z2m: Check Zigbee2MQTT fails to start/crashes runtime | Zigbee2MQTT for possible solutions
[2025-11-28 16:02:21] error: z2m: Exiting…
[2025-11-28 16:02:21] error: z2m: Error: Failed to start EZSP layer with status=HOST_FATAL_ERROR.
at EmberAdapter.initEzsp (/app/node_modules/.pnpm/[email protected]/node_modules/zigbee-herdsman/src/adapter/ember/adapter/emberAdapter.ts:665:19)
at EmberAdapter.start (/app/node_modules/.pnpm/[email protected]/node_modules/zigbee-herdsman/src/adapter/ember/adapter/emberAdapter.ts:1547:24)
at Controller.start (/app/node_modules/.pnpm/[email protected]/node_modules/zigbee-herdsman/src/controller/controller.ts:133:29)
at Zigbee.start (/app/lib/zigbee.ts:67:27)
at Controller.start (/app/lib/controller.ts:101:13)
at start (/app/index.js:149:5)

and MQTT (ver. 6.5.2) shows an error in setting saying re-authentication required.
Log:
2025-11-28 15:53:10: New connection from 172.30.32.2:45280 on port 1883.
2025-11-28 15:53:10: Client closed its connection.
2025-11-28 15:55:10: New connection from 172.30.32.2:44734 on port 1883.
2025-11-28 15:55:10: Client closed its connection.
2025-11-28 15:57:10: New connection from 172.30.32.2:49640 on port 1883.
2025-11-28 15:57:10: Client closed its connection.
2025-11-28 15:58:21: New connection from 172.30.32.1:41435 on port 1883.
2025-11-28 15:58:21: Client 68qhRKZ2iqOBVe1pQFWg9q disconnected, not authorised.
2025-11-28 15:59:10: New connection from 172.30.32.2:40180 on port 1883.
2025-11-28 15:59:10: Client closed its connection.
2025-11-28 16:01:06: New connection from 172.30.32.1:37555 on port 1883.
2025-11-28 16:01:06: Client 4JCr3S4JBM1hDANBDHUXC9 disconnected, not authorised.
2025-11-28 16:01:10: New connection from 172.30.32.2:38494 on port 1883.
2025-11-28 16:01:10: Client closed its connection.
2025-11-28 16:03:10: New connection from 172.30.32.2:33176 on port 1883.
2025-11-28 16:03:10: Client closed its connection.
2025-11-28 16:05:10: New connection from 172.30.32.2:43394 on port 1883.
2025-11-28 16:05:10: Client closed its connection.
2025-11-28 16:05:36: New connection from 172.30.32.1:35059 on port 1883.
2025-11-28 16:05:36: Client 1kmB7m6zjEprnPU2IHUNxE disconnected, not authorised.

I am not able to get all the things talk to each other. Any suggestions what I should try next?

It sounds more like mqtt can’t connect, cause z2m is not running.

I would start by disabling the mqtt broker integration, so nothing is trying to connect to z2m addon.

then see if the z2m will start and run without errors.

someone else had a similar error, it appeared to be the device path. see @ Zigbee2MQTT not starting - using ZBT-2

Thanks a lot for your help.
I stopped the Mosquitto integration and tried to start Z2M. This time it started for a short time and stopped again. The log says htat the herdsman started, but stopped again because it did not find MQTT server.

[17:11:15] INFO: Preparing to start…
[17:11:15] INFO: Socat not enabled
[17:11:16] INFO: Starting Zigbee2MQTT…
Starting Zigbee2MQTT without watchdog.
[2025-11-28 17:11:21] info: z2m: Logging to console, file (filename: log.log)
[2025-11-28 17:11:21] info: z2m: Starting Zigbee2MQTT version 2.6.3 (commit #unknown)
[2025-11-28 17:11:21] info: z2m: Starting zigbee-herdsman (6.3.2)
[2025-11-28 17:11:22] info: zh:ember: Using default stack config.
[2025-11-28 17:11:22] info: zh:ember: ======== Ember Adapter Starting ========
[2025-11-28 17:11:22] info: zh:ember:ezsp: ======== EZSP starting ========
[2025-11-28 17:11:22] info: zh:ember:uart:ash: ======== ASH Adapter reset ========
[2025-11-28 17:11:22] info: zh:ember:uart:ash: Serial port opened
[2025-11-28 17:11:22] info: zh:ember:uart:ash: ======== ASH starting ========
[2025-11-28 17:11:23] info: zh:ember:uart:ash: ======== ASH connected ========
[2025-11-28 17:11:23] info: zh:ember:uart:ash: ======== ASH started ========
[2025-11-28 17:11:23] info: zh:ember:ezsp: ======== EZSP started ========
[2025-11-28 17:11:23] info: zh:ember: Adapter EZSP protocol version (13) lower than Host. Switched.
[2025-11-28 17:11:23] info: zh:ember: Adapter version info: {“ezsp”:13,“revision”:“7.4.4 [GA]”,“build”:0,“major”:7,“minor”:4,“patch”:4,“special”:6,“type”:170}
[2025-11-28 17:11:23] info: zh:ember: [STACK STATUS] Network up.
[2025-11-28 17:11:23] info: zh:ember: [INIT TC] Adapter network matches config.
[2025-11-28 17:11:23] info: zh:ember: [CONCENTRATOR] Started source route discovery. 1248ms until next broadcast.
[2025-11-28 17:11:24] info: z2m: zigbee-herdsman started (resumed)
[2025-11-28 17:11:24] info: z2m: Coordinator firmware version: ‘{“meta”:{“build”:0,“ezsp”:13,“major”:7,“minor”:4,“patch”:4,“revision”:“7.4.4 [GA]”,“special”:6,“type”:170},“type”:“EmberZNet”}’
[2025-11-28 17:11:24] info: z2m: Currently 0 devices are joined.
[2025-11-28 17:11:24] info: z2m: Connecting to MQTT server at mqtt://core-mosquitto:1883
[2025-11-28 17:11:27] error: z2m: MQTT failed to connect, exiting… (getaddrinfo ENOTFOUND core-mosquitto)
[2025-11-28 17:11:27] info: z2m: Stopping zigbee-herdsman…
[2025-11-28 17:11:28] info: zh:controller: Wrote coordinator backup to ‘/config/zigbee2mqtt/coordinator_backup.json’
[2025-11-28 17:11:28] info: zh:ember:uart:ash: ASH COUNTERS since last clear:
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Total frames: RX=48, TX=92
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Cancelled : RX=0, TX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: DATA frames : RX=46, TX=44
[2025-11-28 17:11:28] info: zh:ember:uart:ash: DATA bytes : RX=466, TX=473
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Retry frames: RX=0, TX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: ACK frames : RX=0, TX=47
[2025-11-28 17:11:28] info: zh:ember:uart:ash: NAK frames : RX=1, TX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: nRdy frames : RX=0, TX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: CRC errors : RX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Comm errors : RX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Length < minimum: RX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Length > maximum: RX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Bad controls : RX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Bad lengths : RX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Bad ACK numbers : RX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Out of buffers : RX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Retry dupes : RX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Out of sequence : RX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: ACK timeouts : RX=0
[2025-11-28 17:11:28] info: zh:ember:uart:ash: Port closed.
[2025-11-28 17:11:28] info: zh:ember:uart:ash: ======== ASH stopped ========
[2025-11-28 17:11:28] info: zh:ember:ezsp: ======== EZSP stopped ========
[2025-11-28 17:11:28] info: zh:ember: ======== Ember Adapter Stopped ========
[2025-11-28 17:11:28] info: z2m: Stopped zigbee-herdsman

this would seem to be some kind of network or dns issue, it can’t resolve that server name, or the mqtt broker is not running.

do you have the mqtt broker addon installed, configured and running?

there are 3 components as i understand;
zigbee to mqtt (addon) - interfaces with zigbee and communicates with mqtt broker
mqtt broker (addon) - serves as the bridge/hub for anything needing to send/receive mqtt messages
mqtt integration - translates between mqtt and home assistant

The broker was disabled, as you suggested in your first advice. Perhaps the Z2M had to run first time without the broker running, because now I started the broker and then Z2M and this time it ran without error messages and I can open the web GUI. So many thanks again, you got me over the first hurdle.
However, the devices tab in GUI is completely empty, no devices at all. For devices as such, e.g. sensors , it is of course correct as I had to start with the coordinator and did not add any, but based on my experience with ZWave I would expect to see the coordinator as the only device, but the table in the Devices tab is completely empty. But on the Network tab, when I download the map, there is a yellow dot “coordinator” in the middle and no other devices (as expected). Is this the correct behaviour?

1 Like

The coordinator doesn’t show up as a device

OK, that explains it. I did the whole setup remotely, when I am next time on site, I will try adding a sensor.

Right now I would just like to thank both of you again.

Yeah I think I might not have been thinking clearly on that initial reply, the mqtt broker is what sits in between the mqtt integration and z2m.

I think most addons will need restarted if config is changed, so maybe that is what caused the communication issue.

Glad you got it sorted!