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+--- Thread: Shelly over knx multicast (/showthread.php?tid=6141)
Shelly over knx multicast - gjniewenhuijse - 07.10.2025
Hello,
I used shelly plugs gen3 multiple times to connect to my knx.
Connection is over knx multicast.
This works great, but on one configuration its works only from shelly to lm, not from lm to shelly.
So when i turn on the shelly by the shelly webpage i see the status changed in the lm.
But when i change the groupaddress in the lm my shelly plug doesn't turn on/off.
Any idea why?
In the configuration i have two lm's connected also over multicast. This works great. I entered a encryption key, but the only secure communication is toggled off.
Ip > local and Local > Ip has the right groupaddresses
RE: Shelly over knx multicast - admin - 07.10.2025
Why not use MQTT? There's a ready-made integration for LM: https://kb.logicmachine.net/integration/shelly/
Running KNX/IP multicast over Wi-Fi is not a reliable solution because it uses UDP so messages can be lost.
RE: Shelly over knx multicast - gjniewenhuijse - 07.10.2025
Yes i understand, but how to make the right topic? I want to send and receive.
direction: both
topic name: shellyplugsg3-8cbfea91b494/status/switch:0
in mqtt explorer i see
{"id":0, "source":"WS_in", "output":false, "apower":0.0, "voltage":232.8, "freq":49.9, "current":0.000, "aenergy":{"total":19.000,"by_minute":[0.000,0.000,0.000],"minute_ts":1759821960}, "ret_aenergy":{"total":0.000,"by_minute":[0.000,0.000,0.000],"minute_ts":1759821960},"temperature":{"tC":37.6, "tF":99.6}}
RE: Shelly over knx multicast - admin - 07.10.2025
You need two separate topics for control and status. It should be similar to Shelly Plus 1PM integration:
https://kb.logicmachine.net/integration/shelly/#shelly-plus-1pm
RE: Shelly over knx multicast - gjniewenhuijse - 07.10.2025
Thanks it works over mqtt, but
Why doesn't it work over multicast and then specially from the lm to the shelly? What do i wrong?
RE: Shelly over knx multicast - admin - 07.10.2025
Do you have backbone key set in LM? In this case LM will use secure KNX/IP but will still receive unencrypted messages unless "Enable only secure communication" is on.
Sending multicast messages to Wi-Fi clients might not work depending on your router settings.
Even if you can get KNX/IP to work MQTT is a much more reliable solution for this use case.
RE: Shelly over knx multicast - gjniewenhuijse - 07.10.2025
(07.10.2025, 08:16)admin Wrote: Do you have backbone key set in LM? In this case LM will use secure KNX/IP but will still receive unencrypted messages unless "Enable only secure communication" is on.
Sending multicast messages to Wi-Fi clients might not work depending on your router settings.
Even if you can get KNX/IP to work MQTT is a much more reliable solution for this use case.
Yes, i used a backbone key but "Enable only secure communication" is off.
In the situation it works i have mikrotik router, switches and accespoints.
In the situation it doesn't work i have mikrotik router and switch and Unifi accespoints. Do you have some tips? I like to know why its not working
RE: Shelly over knx multicast - admin - 07.10.2025
Check access point settings, there should be something related to how multicast is handled.