MQTT Architecture?

[kburndred]

I am 100% new to HA but have a strong background with IOT and MQTT.
I would like to read data from an existing MQTT broker.
My expectation is that I can have all the MQTT values show up in HA as ‘entities’ and then use those ‘entities’ in automation(s).
Questions:

1. Is my understanding of how the data will end up in HA correct?
2. Do I need a MQTT Broker in HA?, if so why?
3. Should I be setting up HA to subscribe to topics in my MQTT broker?
4. Where do I setup the MQTT endpoint and credentials?
5. Where do I setup the ‘sensors’ (if that’s what I need)
6. Can I setup a single ‘device’ that will have all my MQTT tags?
7. How do I do that?
   Please advise - Thanks,

[Saoshen]

HA has an MQTT integration, like a connector between mqtt broker and HA.

You can add the mqtt integration and point it at your existing broker.

Most commonly, folks use mqtt in ha, in conjunction with zigbee2mqtt.

That works like this; zigbee2mqtt addon <> mqtt broker addon <> mqtt integration <> rest of HA

mqtt integration @ MQTT - Home Assistant

mqtt broker addon @ addons/mosquitto at master · home-assistant/addons · GitHub

I’m not expert, so I don’t want to speak so much on your specific questions, but the above should at least help until others can better answer.

[francisp (Francis)]

@kburndred

Is my understanding of how the data will end up in HA correct?

Yes, you need to define your entities in .yaml

@kburndred

Do I need a MQTT Broker in HA?, if so why?

Yes, but you can connect to your existing broker. Edit: No need to add the mosquitto add-on

@kburndred

Should I be setting up HA to subscribe to topics in my MQTT broker?

That is part of defining your entities, so yes

@kburndred

Where do I setup the MQTT endpoint and credentials?

Installing the MQTT integration

@kburndred

Where do I setup the ‘sensors’ (if that’s what I need)

Part of defining the entities : MQTT - Home Assistant

@kburndred

Can I setup a single ‘device’ that will have all my MQTT tags?

Maybe, check the docs (probably yes, but without knowing specifics can’t tell if one or more devices)

@kburndred

How do I do that?

By reading the docs linked above.

[Edwin_D]

@francisp

Yes, but you can connect to your existing broker.

To clarify, HA needs a broker to use MQTT, it can be your existing one. There may be some limitations to the authentication methods that the HA MQTT integration will be able to use if I recall right. The integration docs also name two brokers with known incompatibilities.

@francisp

Yes, you need to define your entities in .yaml

You can do it in yaml, but you can also do it in the user interface nowadays.

[francisp (Francis)]

Or create discovery messages

[kburndred]

I have read through the documentation and still don’t have a clear understanding

1. what is the difference between MQTT Integration and MQTT Broker?

I installed the MQTT Integration and it appears to have installed an MQTT Broker

However, there’s absolutely no connection between the HA broker and my existing MQTT broker.
The documentation does not explain the purpose of the HA MQTT Broker

I now have 2 brokers that are not connected and still no understanding of how to get what I want.

The documentation simply does not help.

I have read a lot of posts where people have tried to bridge brokers without success. Seems like a rabbit hole with no clear answers.

Any advice would be appreciated.

[Sir_Goodenough ((SG) WhatAreWeFixing.Today)]

As @Saoshen says, add the HA broker.
Then you can just bridge from your other broker into that one and share whatever you want…

You can also log into the other broker using the integration and use everything from there, but HA can be a bit finicky with that, I find just adding a bridge works better for me.

Look up the MQTT integration in the Home Assistant Docs. They are quite extensive and helpful.

I have a bunch of MQTT in my config, feel free to look at that for inspiration.
https://github.com/SirGoodenough/Home-Assistant-Config

[kburndred]

I added the bridge config to my broker and nothing showed up in HA

Don’t know where to go from here.
Don’t know how to troubleshoot HA
In the past I setup bridging to my cloud MQTT broker successfully so I know how to do it and what it looks like when it’s working.

How do I know if HA can ‘see’ my MQTT Broker?

If I get the bridge to work, will all my tags show up in HA and be useable in automations without any further config, or do I have to setup a device, or sensor or other for each tag?

Thanks,

[Saoshen]

in the mqtt integration (not the addon broker), you can click the 3 dot menu, click reconfigure, then you can point the integration directly to your existing broker (instead of the mqtt addon).

I don’t know if this is better/worse/same as doing a bridge between the broker addon and your external broker.

From what I can tell, the mqtt integration will only support ONE broker.

[kburndred]

Thanks for the information.
I reconfigured the MQTT Broker/Integration

I now have 2 issues.

1. The reconfigure seems to accept an empty password and says that the reconfig was successful. However nothing shows up in HA

2. The password filed keeps reverting back.

How do I know if this method is working?
Where can I see all the tags?

[Saoshen]

In HA, go to settings > system > logs

at the top right you choose from different logs, I don’t know where the mqtt integration logs but I assume in CORE or SUPERVISOR.

You may want to click the 3 dot menu to choose raw logs.

The docs for the mqtt addon @ addons/mosquitto/DOCS.md at f68e2824a0a3c9c4524cf3cc7547397d496c48c8 · home-assistant/addons · GitHub may or may not also apply to getting your external broker setup.

there is also a discord server @ Home Assistant which might have folks that have deeper technical knowledge about mqtt.

Using an external broker does not seem to be very common, so I don’t know if there is much experience to guide you, other than the existing documentations at the HA website and the github repositories.

I don’t know if this is relevant, but FWIW this is how the zigbee2mqtt publishes to the mqtt broker addon (which communicates with the mqtt integration);

[2025-12-10 12:37:37] info: 	z2m:mqtt: MQTT publish: topic 'zigbee2mqtt/Air Sensor 1', payload '{"elapsed":9923,"humidity":35,"identify":null,"last_seen":"2025-12-10T12:37:37-06:00","linkquality":172,"pm25":1,"temperature":20,"update":{"installed_version":16777233,"latest_version":16777233,"state":"idle"},"voc_index":98}'

[pkscout (Kyle Johnson)]

I use an external MQTT broker in HA with absolutely zero problem. Once you connect to it using the MQTT Integration, everything behaves exactly the same as if you were running the HA broker add-on.

What exactly are you expecting/hoping to see in HA after you do that. Unless you have MQTT topics that have the HA auto discovery in them, you won’t see any new entities in HA. You would have to set them up by hand and then restart HA (I think others have linked to the docs for that already). If you want to see if the integration is properly connected to your MQTT broker, check out this thread on how to send something manually to the broker and listen to a topic:

How to listen to MQTT topic under Dev Tools?

Can someone please tell me where this functionality is now? [image] Thanks

[kburndred]

I pointed HA to my broker and it said success.
However absolutely no indication that it was working or not.

My MQTT broker has hundreds of tags.
I am expecting HA to allow me to use all of them in automations/dashboards etc.
So far I have manually added around 10 or so.
Is there a way to have all of them just show up, without having to manually add each one?

Thanks,

[tom_l]

@kburndred

Is there a way to have all of them just show up, without having to manually add each one?

Only if your devices publish discovery messages to the homeassistant discovery topic. See: MQTT - Home Assistant