Conflicting DHCP when Deco in AP mode ?
Today I ran into an issue which made me almost cringe.. as I hadn't expect this to happen, considering I've been working in the IT networking business for over 30 years..
I had recently purchased a Deco M5 mesh set with 3 nodes and setup as AP access points, because I alread have a decent router from my ISP (Zyxel EMG2926). This has been working fine for the last 6-8 weeks and nothing to complain about.
Last night, for some strange reason my router rebooted and I lost Internet connexion from everywhere, including my wired PC's which I use every day to work from home.. So getting back internet was critical to me and I tried the quick obvious options like rebooting the router and also reseting to factory the router, then reloading the configuration I had on backup.. To no avail, I wasn't able to get an functional internet, still the router diagnostic was able to ping any IP address outside my network.. Since I needed to work and support clients, I disconnected the Zyxel router and put back the Mercku M2 Hive base I had prior to the ISP router and after 5 minutes, was back into business.. (The Mercku is also a Mesh Wi-Fi system with 4 Bee nodes, albeit it wasn't working to my entire satisfaction, thus the purchase of the Deco M5).
Having spend the morning with work, I had hope the issue with the router might have been on the ISP side, so tried to set it back in action. Result was identical and nothing was really working.. Put the Mercku M2 back for the PM as I had a support call and did need internet ASAP.
At the end of the PM I got back to my router and it was so weird that I even tried to reset the Zyxel for the n-th time and start from scratch.. What puzzled me was that it was working if I forced my computer into fixed IP address, and even with DHCP Mac address reservation, the router wouldn't route my requests properly to the internet.. Looking at the IP addresses in the config made me think that router was totaly corrupt and crazy.. The router's IP is 192.168.127.1, but returns 192.168.127.102 as gateway and .254 for the DNS server, which is even crazier.. This is when I started to scan my network for rogue devices with my Android smartphone, but couldn't find anything suspicious. I've a lot of IoT devices and aside of the 3 Deco M5 AP's, there was nothing un-usual. However, the .102 IP address made me tick and look closer at the Mac Address, to finally discover that the main Deco M5 unit (the one connected by Cat5 cable to the switch) was the culprit.
For some obscure reasons my Zyxel router was thinking that the Deco M5 AP unit was the master DHCP on the network, despite TP-Link saying in their documentation that it is not the case when in AP mode.. As a proof, my Mercku M2 router had no issues at all with that and was perfectly handing over IP addresses to all devices..
Has anyone run into such a situation with another HW router ? getting conflicting DHCP server mode while the Deco M5 is in AP mode ?
I fixed my problem my disconnecting the Cat 5 cable temporarly from the switch, rebooted the Zyxel router and voilà.. after it was back as 'master' DHCP, I plugged the Deco M5 back and all was working as before.. But I'm really curious about that strange behavior.
Any comments are welcome on this.
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@TP-Link_Deco when are you going to release the promised 1.6.0 firmware to fix this crap?
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Bin their junk and move on. I sold mine and got some ASUS devices (ASUS ZenWiFi AX (XT8)), does exactly what they are supposed to in AP mode. I.e. nothing but wireless transit.
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This was raised on 2019-02-19, and 25 months in @tplink have done nothing at all. not even a toggle option to fully disable network services when in AP. They don't even acknowledge that this is an issue. No one wants or expects any form of network service when in AP mode, yet this is ignored by the vendor. The Deco range is junk, poor software, low volume of updates and so basic in terms of configuration options for the price.
This problem won't be fixed, it's over 2 years now and it is clear from a product perspective they don't see this as an issue. Sell your devices and go elsewhere. ASUS have some nice powerful mesh kit.
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Update：
[Feature Request] Smart DHCP on/off switch under access point mode
Solution:
Many models have added the option to turn on/off smart DHCP under AP mode and please refer to this link to make sure the Deco firmware is up to date.
Deco Firmware Updates Adding Signal Selection and VPN for Multiple Models
Some Background Introduction of How Smart DHCP Works on Deco:
With the built-in smart DHCP, Deco will send a DHCP server request when joining a network and check if it can receive the response from a DHCP server. If there is a response, Deco will think there has been a DHCP server in the network already, then no need to enable its own DHCP server. Otherwise, there is no DHCP server detected in the network, then it will turn on its own DHCP server.
The DHCP server request will be updated every 60s which means if the main router has not fully activated for the first 60s, once it is activated and could respond to the DHCP request, the DHCP server on the Deco will be automatically turned off.
Some users might complain why my Deco left its DHCP enabled for more than 1-2 hours. After further troubleshooting with more users, we find Deco uses “smart DHCP”, while the main routers have their own special DHCP settings, for example, “Assign IP address only when there is no DHCP server”, quite the same as Deco right? They will also search whether there is already a DHCP server or not. Now the main router detected Deco had enabled its DHCP firstly, so it quit, leaving all the clients no choice to continue getting IP from Deco.
[Successful cases]
An old switch turned out to be the second DHCP server
The Apple capsule turned out to be the second DHCP server
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It's over 2 years since this got reported and you're still telling people "engineers have been informed", yet nothing at all is made available. You don't even share an ETA for 1.60 or offer some beta firmware for people to actually test FOR YOU, and in the meantime get some potential relief from the mess this feature creates.
25 months for essentially nothing.
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@GPGeek totally agree with all the posters here : I've had problems with M5 deco's several times in the last few weeks, each time them causing DHCP problems in AP mode and kicking my (Huawei) router off the 192.168.8.x range onto 192.168.9.x, only solution being to disconnect the decos and reassign. Shocking that such a simple, core, function should be wrong for so long and that denial and failure to address be the response. These are going back and another warning not to trust cheap tp-link gear. Over the years I've phased out over TP-Link AP point hardware - guess it's my fault for getting bitten by this again.
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winter98 wrote
I've had problems with M5 deco's several times in the last few weeks, each time them causing DHCP problems in AP mode and kicking my (Huawei) router off the 192.168.8.x range onto 192.168.9.x, only solution being to disconnect the decos and reassign.
Are you sure it is not different issue? In all my tests when ISP router was off but Deco stayed on, Deco mesh keeps assigning IP addresses in same IP range ISP router did.
My home network runs on 192.168.0.* range, ISP router is 192.168.0.1, Main Deco is 192.168.0.131, when I power off ISP router and reboot desktop, this is what desktop gets:
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@Alexandre. thanks for responding - yes. Each time this happens I have to disconnect the decos from the network for the router to return to the 192.168.8.x range - otherwise it goes onto 192.168.9.x and if I attempt to force DHCP to the 8 range it refuses.
The weird thing is that if i use fing to scan the network none of the deco's seem to have taken the 192.168.8.1 address - but they do seem to block the router / force it to go to another range. Turning them off / disconnecting the ethernet cable and restarting the router does work each time.
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I see. So it is ISP router that moves to different IP range, not Deco mesh.
Check your router settings - perhaps, it sees different DHCP server (Deco) and moves to another IP range to avoid conflict. If it does, there might be a configuration setting in a router to prevent that from happening.
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