Open Thread Border Router documentation mentions non-existing dummy device ‘/dev/ttyS3’ for networked OTBRs / RPI4?

[jbattermann (Joerg B.)]

I’m trying to set up a network-connected (and only network, no USB) SLZB-06M as OTBR for HA on my RPI4 (running HA OS 15.1) and the add-on documentation states “[…]When using a network device, you still need to set a dummy serial port device, e.g. /dev/ttyS3. […]”:

… but when configuring the 'network_device ’ setting and trying to use ‘/dev/ttyS3’ for the 'device ’ parameter, I get an error stating "Failed to save add-on configuration, Device ‘/dev/ttyS3’ does not exist in OpenThread Border Router (core_openthread_border_router). Got {‘device’: ‘/dev/ttyS3’, ‘baudrate’: ‘460800’, ‘flow_control’: True, ‘autoflash_firmware’: False, ‘otbr_log_level’: ‘notice’, ‘firewall’: True, ‘nat64’: False, ‘network_device’: ‘192.168.7.245:6638’} "

And sure enough, when SSH’ing in and checking for /dev/ttS*, there’s nothing there:

Using /dev/null also doesn’t work because saving returns an error saying “Failed to save add-on configuration, Device ‘/dev/null’ don’t match the filter subsystem=tty!”.

So I tried one of the ones listed under /dev/tty*, i.e. /dev/tty60 as per

… but same / similar thing: "Failed to save add-on configuration, Device ‘/dev/tty60’ does not exist in OpenThread Border Router (core_openthread_border_router). Got {‘device’: ‘/dev/tty60’, ‘baudrate’: ‘460800’, ‘flow_control’: True, ‘autoflash_firmware’: False, ‘otbr_log_level’: ‘notice’, ‘firewall’: True, ‘nat64’: False, ‘network_device’: ‘192.168.7.245:6638’} "

Sooooo… how DO I configure the OTBR add-on correctly for a network’ed device and when the system has seemingly no dummy /dev/ttyS* device(s)?

[wmaker (Tommy Long)]

@jbattermann

SLZB-06M

I have not used this device, but looking at this guide, it says: “Due to HA configuration limitations, you still need to have some USB device connected even with a network connection”.
Maybe try the /dev/ttyUSB0 and see what happens.

[jbattermann (Joerg B.)]

Thanks @wmaker for chiming in & well yeah… they’re just re-phrasing the odd limitation of the OTBR add-on requiring a /dev/tty* device even when using the network_device functionality. And that’s my point/question… the documentation mentions a somewhat specific “dummy” device that’s not there.

And having to have a spare and then plug in some… any rando USB device just to overcome some odd … bug (?) of the add-on / its configuration / save logic just seems wrong/odd. If anything I’d be fine with some proper dummy device or /dev/null or somewhat, but there is a /dev/tty(s) check in place… so not sure what’s up with that / and the current documentation.

[ArunGupta]

Hi,
I have recently setup OTBR using this device and can guide you extensively with setup and troubleshooting. This device works perfectly with HA even over Wi-Fi/Ethernet.

Thread works only over IPv6 and absolutely requires mDNS for name resolution. Please ensure that IPv6 is enabled for your Home Assistant network and there are no VLANs. mDNS doe not work over VLANs by default. There is absolutely no need for any kind of DHCPv6 server on the network, we just need to make sure that IPv6 is enabled. That’s it.

Now, setup the SLZB-06 as Matter-over-Thread device. I am assuming that you have already setup the networking to either Ethernet or Wi-Fi. Either will do. After setting up the networking and assuming that you did not change the mDNS name of SLZB-06, you should be able to access the SLZB-06 web interface at http://slzb-06.local

I would recommend assigning a static IPv4 address to the SLZB-06. This will make setup easier.

If this works, then we proceed to next step of configuring OTBR.

For initial setup, let’s leave the port at 6638 and speed at 460800 as these are the defaults.

This is a picture of my setup from SLZB-06 dashboard:

You can see:
Radio Mode is Matter-over-Thread
MDNS address: SLZB-06.local
In socket connected, it says Yes, I client. This is HA OTBR. Initially you will not see any client connected, but we will soon change that…

In HA, install the Open Thread Border Router add-on. Make sure to install the Add-on. This will automatically add the OTBR integration, The integration is not used. All configuration is done from the OTBR add-on.

Open the HA OTBR configuration page and set the following:

The add-on configuration page shows all the available serial ports, used or unused. As you can see, I am using one serial port for Z-Wave stick. So, I randomly selected /dev/ttyS1. You can choose any unused serial port.

I selected a baud rate of 460800 which matches the baud rate of SLZB-06. Hardware flow control is off. Next we configure the Network Device:

I have assigned a static IPv4 address 192.168.250.176 to the SLZB-06 device and port is 6638 which matches what we have for SLZB-06 device. This is extremely crucial that the SLZB-06 IP address and port matches the IP address and port in HA OTBR add-on.

Disable Automatically Flash Firmware as this cannot be used for SLZB-06. Leave the log level at notice. Turn on the OTBR firewall. Turn off NAT64. Save the configuration. Start the OTBR add-on. Wait for few minutes and check the status by refreshing the OTBR add-on page. If the add-on was able to establish communication with SLZB-06 device, the add-on will remain started, otherwise it will shutdown. If you check the log, it will show the last line as shutting down mDNS (or something like that).

If the connection is established, then in HA, go to Thread integration and click Configure and the TBR should be visible.

If you did all this setup and OTBR add-on fails to stay started up, then please post here and I can help with troubleshooting.

Hope this helps.

[daniel_drp (Daniel)]

i have the same issue.
When trying to setup the OTBR, the list of devices is empty.
It also does not work via yaml.

I tried to attach USB-Dongles (Keyborad) and USB Drives. I also set the SLZB-MR1 (might work the same as SLZB-06M) to USB mode.
I use HA on RPi4 and also tried a fresh installation on another RPi4 with the same issue.

Your instructions seem pretty fine, but it does not work if its not possible to choose a dummy device via radio button or yaml.

[Ewster (Ewen Bell)]

Same issue here with SLZB-MR3. No tty ports to choose from, so the OTBR installation goes nowhere.

Check on Github and the issue has been (automatically) marked closed due to inactivity…

OTBR Add-on doesn't work without (dummy) USB Device / Documentation mentions non-existing one (for HAOS)

[sataroo]

I hade same issues with SLZB-MR3 in OTBR and tty etc. whenever I start the OTBR with the correct config it stops automatically.

Then, I enabled the ipv6 on my ISP router. and configured my Proxmox network configuration to accept ipv6 and give my Home Assistant OS an ipv6 address. after that I rebooted and deleted everything and started again and it worked.

I used ChatGPT to assist me with configuring ipv6 in proxmox for my home assistant. the ipv6 locally was enough.

and for making it work later with my devices I followed a Youtube tutorial for a russian lady for setting up SLZB for Matter over thread. I needed my alexa Echo Dot 4th generation to connect my Zigbee devices to my ios HomeKit.

[ThatBoyPamp (Pamp)]

Hey everyone, I hope you have found a solution by now but if you haven’t I just wanted to let you guys know I found something that worked for me.

I had to take the sd card out of my Pi and change a couple of things in the config.txt file. There are two lines that need to be uncommented.

enable_uart=1
#dtoverlay=rpi-rf-mod

Once I did that I had to update my firmware on my SLZB MR4 because I was behind a couple versions but then I had my serial device showing up, where I previously did not, and I was able to connect and start setting up devices!

Hope this helps someone!

[smrky (Martin)]

Thanks for sharing this workaround! Works for me just fine.

[Stephan0815 (Stephan)]

is there a way to create a workaround on proxmox? just adding a serial port and choosing this doesnt’t work

[M_Chyla]

Worked for me on RPI400

Thank you very much!

[DRchem (Dominic Ryan)]

I am running HA on a docker container in a QNAP NAS

• Installation method Home Assistant OS
• Core 2026.2.2
• Supervisor 2026.02.2
• Operating System 17.1
• Frontend 20260128.6

I installed a SLZB-06M, it is plugged into a switch with POE+

Model: SLZB-06M
Radio Core
Status: On-board On-board
Flow control: SW -
CPU model: EFR32MG21 ESP32-S3
CPU cores and clock: 1 @ 80 MHz 2 @ 240 MHz
Flash memory: 768 KB 16Mb
RAM memory: 96 KB 520Kb
SoC temperature: 42.36 °C 44.44 °C
Firmware version: 20241105 v3.2.4
Latest FW check: 19/02/2026 Unknown

Radiomodule mode:	Matter-over-Thread
Connection mode:	Ethernet mode
4G/LTE status:
IPv6	On
Ethernet connected:	Yes
USB mode:	Debug port
Wi-Fi client turned On:	No
Wi-Fi AP turned On:	No
Socket connected:	No
Device uptime:	0d 01h 33m
Socket uptime:	Not connected
mDNS address	SLZB-06M.local
Internet access	Yes
Automatic Zigbee Update	Off
VPN Enabled	No
VPN Connection Active	No

Mode is thread, device flashed.

When I try to add integration → open thread border router, it only asks to put in the url for the REST api. I put in the IP4 address:6638, which is what is listed under the radio mode.
I only get connection failed.
I have tried power cycling everything multiple times.
Any suggestions would be most welcome.
Thank you all

[ArunGupta]

Sorry for late reply. Open Home Assistant. Go to Settings → Apps. Install Open Thread Border Router as an app (formerly the Apps section was called Add-ons). If the OTBR is installed and configured correctly as an app, the OTBR integration will automatically appear in HA.

I have also disabled IPv6 in SLZB-06. IPv6 needs to be enabled in HA and the network that HA connects to.

After adding OTBR as an app, open its configuration page and make changes as per the screen capture in my post. You will need to select any unused tty port. Select a baud rate that matches the SLZB-06 device. In the Network Device, enter the IP address of SLZB-06:6638. Save the configuration and start the app. The OTBR integration will automatically show up in HA.

Hope this helps.