@Kevin_Z 

Is there any vendor update. This is a significant bug, and your product isn't cheap.

Surely disabled means disabled and that ought not to be an issue to implement??

@Kevin_Z 

Hey Kevin, thanks for the reply.

I don't think it needs all those things you requested. As per the 3rd post from you in the thread "FYI, the DHCP server is disabled in AP mode, while if the connection drops out, the DHCP server on the Deco will turn on automatically temporarily so that you still can manage it with the Deco app; and it will be disabled once the main router back to work."

It is precisely this that I, and others, want to fully disable. I don't want a random DHCP server popping up on my network at ANY point at all. So if I disable DHCP on the Deco, I just want that. A fully disabled DHCP server.

No need to generate diagnostics, or send diagrams as it is clear the current does turn DHCP on. Can you implement a "Fully disable DHCP" feature please?

@Kevin_Z It is a total lie as far as firmware 1.3.1 is concerned that the DHCP server is disabled in AP mode.  And this lie is causing a lot of mayhem.  It is so annoying that I demand a firmware release to fix this problem yesterday not tomorrow.

@Kevin_Z 

Could you please drop a response to this. I get that you are looking for solutions however I really think it is as simple as enabling the DHCP server to be fully disabled.

This "smart DHCP" is killing networks when it decides to come on. No need to look into why it ends up becoming active, we just want it NEVER to happen.

Leave those who know what they are doing to manage their own network.

@phillip_mcmahon 

Because @Kevin_Z 's organisation TP-Link is nowhere near treating this as requiring a fix, let alone an urgent one, it would be worthwhile trying this workaround in the meantime, it helped with my Deco M5 units, so perhaps may work with Deco M9 plus too. The discussion below assumes your router device runs your DHCP server too, a common use case in home networks at least, please adapt the discussion to your scenario if that's not the case:

When setting up the main unit in the Deco app, connect it to internet just not in your LAN so when its DHCP server takes over the world, it doesn't affect your LAN. One could do that by temporarily disconnecting all ethernet LAN connections from the router except Deco's, though it won't help with wireless devices connected to that router so also change the SSID at the router before connecting Deco for the first time or switch off the wireless function at the router temporarily; you could also use a different router temporarily which isn't on the same network segment as your LAN and has only the device with the Deco app and Deco connected to it on a different SSID from your main router's. Once Deco is configured, switch it to AP mode. Doing this so far does not stop Deco trying to take over DHCP, so the next steps are important.

"Disconnect Deco from your network by unplugging its cable at router/switch, power it down while it is configured as AP, restore all your LAN connections at the router if you had unplugged them before setting up the Deco and putting it to AP mode, restart your router so that it can again claim its rightful DHCP master status in the absence of Deco, then connect the Deco's cable to the router/switch and power it on."

The difference between this and the initial power on of the Deco is that you are now powering the Deco on while it's already configured in the AP mode. Fingers crossed, this will lead to the Deco not trying to take over DHCP, at least as long as your desired DHCP server is up. When setting up the Deco initially, it is not in AP mode, so it forces its DHCP server on the network, which isn't desirable, so what I'm suggesting is a workaround only until the slow acting TP-Link do something property about this.

Not powering down the Deco after putting it to AP mode does not disable its DHCP server. But because your router now needs to establish itself as DHCP master again, the router needs to be restarted too before Deco is connected and powered on again.

I would even say that if you have DHCP snooping facility, use that to discard all DHCP packets from the rogue Deco.

Fix this TP-Link, seriously.

@MDec 

@Kevin_Z 

Many thanks for the reply and the setup and configuration tips.

My network doesn't use my router for DHCP, it's just doing firewall and router business. I have a domain controller that provides DHCP and DNS services. Things ordinarily work fine, and with living in an old house over 4 floors almost everything is on the mesh network so when it goes wrong it's a pain.

The DC, DHCP and and DNS server are not on the mesh network, they are connected directly to a switch into my router.

There was a time these services were also mesh connected. Not a good idea as rebooting the mesh nodes also was a cause for the "Smart DHCP" feature to rear it's ugly head.

The consistent factor causing this problem to appear, was that DHCP allocations were set to a low value, 5 minutes. On a few occasions when I've applied major Windows updates the DHCP service was not available and devices start requesting leases during that time. This meant I encountered the Deco "Smart DHCP" behaviour. I've since extended my lease time to be 8 hours which means I avoid this with some margin for error too. Clearly such a low lease time wasn't helping the situation, although I should be able to set it to whatever I want. It's my network after all. Are you listening TP-Link!

I just want the simple option to fully and permanently disable DHCP. I'm amazed TP-Link don't see the issue this can cause on a network and are asking people to install wirekshark and perform packet captures and mess around with low level diagnostics. Whatever causes it, isn't the issue, it's the fact it can enable a previously disabled service.  It's just a very bad design decision, and one that's kept hidden making it doubly worse.

@Kevin_Z Please can you push to issue what must be a simple fix to remove this behaviour.

@phillip_mcmahon 

While setting the lease to 8 hours should help, it depends upon how much time had elapsed since the last lease when you happen to patch Windows (in your case) leading to DHCP server downtime.  If it is towards the end of those 8 hours, a lease renewal may get requested whilst the DHCP server is down and so the Deco would kick-in.  The workaround pending Deco's proper fix in firmware is to use DHCP snooping to prevent Deco taking over - if you have a managed switch as opposed to an unmanaged switch, it probably has that option.

The essence of the post I made above is that every time Deco takes over DHCP even when in AP mode, one needs to power off Deco, restart DHCP server (whether in router or separate, wherever it is) so it can advertise itself as DHCP master and allocate IP addresses, then power Deco back on.  Not convenient, not ideal, not desired, hence TP-Link need to stop Deco doing this.

The main conflict in the observation of @Kevin_Z  and so many customers is that the customers have observed that even in AP mode, once Deco takes over DHCP, it never goes back really unless powered off and subsequently 'powered back on not before there is another DHCP server up and running' while @Kevin_Z /TP-link claim that Deco will disable its own DHCP server as soon as there is another DHCP server on the network. Regardless of this, the leases it has granted in the meantime are now problematic.

Some people have mentioned though they have DHCP server implementations running which effectively do not care if Deco DHCP server is running on their network when that implementation's DHCP server starts up and they override Deco, but that's not the case with my router's DHCP implementation, nor does it appear to be the case with so many customers' DHCP implementations.

Just provide an option on the app to disable DHCP server TP-Link, thank you very much.  Ah, and also on the web browser UI please.

@MDec 

Totally in agreement. I was just explaining my setup and situation.

8 hour lease times makes a difference. I might get unlucky but probability is in my favour.

Doesn't change the fact this shouldn't happen. Disabled should mean exactly that.