TP-Link Deco M5, no internet no local connection thru ethernet port

Please Help,

I have many TP-link Deco M5 mesh network units in different locations and I have been very satisfied with this system. In two locations I run HA in that environment

However I found one very bad feature in these for home assistant. The problem is when you lose your internet connection. I had my doubts here - there were signs that this was not probably working. I started to check that today. This is what I found:

When I pull my ethernet cable out from my main Deco unit (Bridget thru the modem), basically all the mesh is still working “locally”. I can see all the devices connected to the mesh and I can connect them and ping is working - except one:

RPI handling the automation is connected to the main Deco with ethernet cable on the other ethernet port (there are two of them per unit), once the internet is lost the other ethernet port loses the connection to the mesh also, no ping no active device in the mesh. No working automation either?

In the other Deco units in the same network (not the main Deco) all the ethernet ports still work and the devices are connected and you can ping them.

I have Deconz Raspbee shield (no wlan?) ->solution is not using wlan here with RPI, it needs to be a cable and it needs to connect the main Deco.

Any idea is my main Deco OK or is it not working as it should?

I will highly appreciate all the answers - please help.

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Hi there, have you found a solution to this? My main Deco M5 unit is exhibiting the exact same problem. The other Deco units have 100% functioning ethernet ports when the internet is disconnected; all ethernet devices are still connected to LAN. The main unit however seems to kick off all the wired connections to it. I have a network switch with 5 devices connected to it, which is connected to the main Deco’s remaining ethernet port. Works perfectly fine when internet is connected, but everything connected to the switch (which is connected to the main Deco unit) disappears from the LAN when internet is disconnected. Extremely frustrating if this is a hardware limitation.

Unfortunately not - I contacted TP-Link support and they were all over. I documented the case in many ways with many units for them and their answers depended on who was on the other end. They kept asking me to make different tests even all my documented tests proved my point.

I said them it is time for them to make tests and solve the problem instead of tease their paying customer (I have 10 units) - I got finally so frustrated to them that I kindly asked them to destroy all my posts because they did not help at all.

I think the only solution is to add one more Deco connected with wifi to the main Deco and use those ethernet ports to connect your equipment.

I would appreciate a lot if you could also complain TP-Link this very bad feature. And least they could do is to explain the behavior in their manual …

I think this is very bad feature, because you do not figure it out easily and for instance for me the whole automation is based on the idea it being not dependent on working internet - this totally destroys that goal.

Sorry I could not help more.

One workaround would be to avoid having the Ethernet port with your Internet box going down, even when the internet box is down. Eg. by putting a small ethernet switch in between. I suspect, the Deco has some king of limitation/bug in handling the situation where one of the 2 ethernet port goes down.
Can you try that ?


Thanks for your response!

Unfortunately I do not have any extra switch available and on the other hand I am pretty much done with all this testing with this unit as the fact is that it does not work as you would expect.

However I am not sure does this cover your test suggestion:

This main Deco does not work when both ethernet cables are connected in both ends. The one which goes thru modem to Internet is connected in modem end “switch” - when I pull the cable from modem to wan out (Deco cable is still connected to modem “switch” and the power is on), LAN stops working in the second main Deco ethernet port.

Did that answer to your question?

I just tried this, put a switch between the modem and the main deco, and that did not resolve the issue. It seems any Deco unit that is connected to the modem will experience this issue with the available ethernet port.

Hey thanks for joining the team! :wink:

Yes sure I will report if I get this solved. I hope you will also let me know if you end up to the solution.

I also hope you will end up to better results with these “senior engineers”; for me they were totally useless. But I think it is always good when more people complain when there really is something to complain about.

For what it’s worth I have a Deco mesh, but I have a separate router so none of them are connected to the modem. I haven’t see anything like this, and my internet has been going down pretty regularly lately.

Thanks for your response!

OK - yes I think it works as the Deco is used as AP-mode (access point). I have never tested that - because I will not use AP-mode.

However I think we discuss here the problem using unit in router-mode - the default setting. And the problem is with main Deco not the slaves connected with wifi to the main Deco.

As far as I understand you lose many nice features administrating your system with AP-mode.

In router mode you have really nice way to make adjustments and monitor your mesh remotely using mobile app.

The senior tech just sent me a firmware update v 1.4.4 Build 20200318 Rel. 58040 which according to the email is a “debugger”? We have scheduled a teamviewer chat later this evening where she will remote into my computer to reprogram the LAN port. This was her explanation:

Regarding the issue you mentioned, it’s normal that you won’t have access to the NAS when the main Deco is disconnected. The main Deco does require an internet connection to decide the role of its two Ethernet ports. Once it gets internet connection from one Ethernet port, the port will become the WAN port automatically. If the WAN port is disconnected, the main Deco will keep searching for a connection and won’t decide which port is WAN & which port is LAN until it gets an internet connection.

We can help you disable the LAN/WAN auto-detect feature with a debug firmware.
Please download the debug firmware from the link below and install it as per the attached installation guide.
Debug firmware for Deco M5:

After that, shall we arrange a remote session via Teamviewer? We can help you fix the port which connects the NAS as the LAN port so that it can assign an IP address to your NAS device.
As for the remote time, we’re available from 9AM to 20PM, UTC +8 (Beijing Time, China). Please kindly inform us when you’re available.

Thanks and look forward to your reply. Have a nice day!

From what I understand, once you connect the modem to the main Deco’s ethernet port, it will then know to distinguish the port as WAN and other port as your LAN. But once you disconnect the internet, the main unit will not know how to distinguish the two and will continue searching via both ports for the WAN connection (thereby making both ports WAN ports), and as a result the LAN device is kicked off of the network. Since the other slave units do not have to make this differentiation, both ports on them will remain as live LAN ports on the local network even if internet is disconnected.

The goal of the teamviewer remote session with the tech will be to disable this “automatic assignment” of the ports so that one port permanently remains as the WAN port, while the other port will permanently remain as the LAN port. This way the main unit does not need to “search” via both ports for the WAN connection once internet is disconnected, and will know to keep LAN persistence on the other ethernet port.

At least that’s my interpretation of the tech’s email. We’ll see if our session actually bears fruit.


Thanks for the update!

That’s good, let’s wait and see how it works. Sounds like good service for you from TP-Link side, maybe you have been more polite than me :smiley:.

I sure understood that pretty much as you explained was the reason and good if they can do something for it.

On the other hand I think it should be an option to pick the current wan port as fixed until you change the setup.

But yes, let’s see what happens …

Just wanted to report that the senior tech resolved the problem for me! Under normal circumstances, the LAN port on the main deco unit functions as it should now, with or without internet connectivity. That is until the Deco is rebooted. If rebooted, all you need to do is allow your Deco to reconnect to the internet first, then enter two lines of code in command prompt to restore the LAN persistence. Not the perfect solution, but I’m not disappointed at all either. I hope this helps.

Thanks for the update again!

Very good you found a solution for you even it is not perfect as you say.

However I think I skip this solution; I need something stable when for instance my automation takes care of heating far away where for instance pipes will freeze. I have UPS etc. but still if main Deco would restart … not a good idea :neutral_face:

Did TP-Link say anything else of fixing this problem. Any coming firmware update to take care of this?

Meanwhile my solution is not to connect anything to second port. I use an extra Deco to take care of that (cost me 45€ a piece)

Yep, very same problem here, but i’m using the E4 model. No internet connection = chaos in LAN. I hope they fix this asap.

Thank you! I have been trying to figure out why my Deco M5 won’t connect locally to devices over ethernet when my isp has an outage. Personal I don’t think it is worth going through the trouble of trying to fix the deco, I’ve got a mini pc coming and I’ll be using pfsense from now on. Let me know if you find a way to broadcast the 2.4ghz and 5ghz on different ssid’s.

@vamazon Can you share that code? I am having similar issues.

Hi All,
I got the same issue.
I have cable to a device on LAN connection and a cable to a ISP Router.
When I lost internet connection, or disconnect the ISP Router I lost connection with the LAN device too.

Ok guys, registered just to comment here and get notification when and IF we get a solution to this.

I too have this exact problem, DECO 5 mesh of 3 devices. My Main PC which is connected via Ethernet cable to the second LAN port on the main deco gets disconnected when my ISP is down or whatever. It will NEVER come back, i need to completely disconnect from power and reconnect so it reboots and it will work again.

We need TPLINK to acknowledge this and most importantly FIX IT. We need an option in MAIN DECO config to select which port will be WAN and which port will be LAN, simple as that.

In the mean time i can also confirm that latest firmware, that is: 1.4.9 Build 20200924 Rel. 60170 released a few hours ago didn’t fix it.

However, i found this option on the control panel via Web Browser, called “WAN Unicast”

Can someone tell me what the hell is it? No google result. Sounds like the option we need…

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Lets bump this one until we get a reply from TPLINK.

Any updates on this one? I’m using 1.5.1 Build 20201022 Rel 66804. Still seems to be a problem in Mar 2021. Up until today, I’ve been using 3 Decos in an AP mode without a problem. As soon as i installed a 4th Deco in star-configuration (Router>Deco>Switch>Decos) and switched to Router-mode, my devices stopped seeing the wired ethernet connection.
Update: Troubleshooting my device/PC fixed Gateway connection issues. Now, my device is seeing ethernet again. I’ll report back if this problem returns after power disruptions.