Conflicting DHCP when Deco in AP mode ?
Conflicting DHCP when Deco in AP mode ?
Conflicting DHCP when Deco in AP mode ?
2019-02-18 23:44:39 - last edited 2019-02-19 00:01:07
Model: Deco M5
Hardware Version: V2
Firmware Version: 1.2.4

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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9 Replies
Re:Conflicting DHCP when Deco in AP mode ?
2019-02-20 06:51:21

Hello, there is no DHCP server existed when Deco unit works as the access point.

It is suggested to confirm the operation mode of the Deco units. And the current network topology/diagram will be useful. 

Besides, if the issue happened again, it is suggested to check the IP address and default gateway of your devices which connect to the main router and the Deco unit separately.

Note: How to get them: https://www.tp-link.com/en/faq-838.html 

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Re:Re:Conflicting DHCP when Deco in AP mode ?
2019-04-13 17:44:36

I had this issue too, mine is Deco M4 with the latest firmware, set as AP mode, everything working fine until my router reboot, this Deco unit seems will take over the DHCP role once it found the main DHCP isn’t available, just like what Asus did, which is a good thing but it doesn’t restore unless I switch all Deco units off and on again.

 

It seems only occur when you have something connected on the LAN interface behind the Deco unit, I mean if I just plug in 1 LAN for Ethernet backhaul it’s ok, once I plug-in another LAN to connect eg. TV box, and the main router turned off, it will “intelligently” take over the DHCP role, and never go back.

 

As as an IT guy, I can confirm this is Deco’s problem, it shouldn’t have the DHCP Overriding function on, please tell your team to fix it by just turning it off, pretty simple, doesn’t take months to do it, right?

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Re:Conflicting DHCP when Deco in AP mode ?
2019-04-14 20:04:53 - last edited 2019-04-14 20:05:44

Me too, i'm trying to solve this.... What happens to the DECO in AP mode when main DHCP disapears?!

 

In AP mode, they have simply to follow the DHCP not replace it!

 

here my thread, first i tried to solve this issue by making DECO main DHCP, but discover other issues, finally came back to AP mode but allways this issues, tried with my internet BOX to be DHCP same issue, try with another router same issue.

 

The only "solution" i found but not really good because this is old materials (don't support high speed internet bandwith) is with a DDWRT firmware on WRT54G, the DHCP server seems to me more authoritative and erase DECO adressing when coming up....)

 

Hope TP link will solve this quickly, i have 6 DECO M5 at home....

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Re:Re:Conflicting DHCP when Deco in AP mode ?
2019-04-17 05:04:07

Hello!

 

Why TP-Link don't take the problem? I've reproducied this easly in AP mode!

How to completely disable the DHCP of DECO? firmware in progress? need informations please!

 

Thanks 

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Re:Re:Re:Conflicting DHCP when Deco in AP mode ?
2019-04-18 08:48:13

heidarren wrote

I had this issue too, mine is Deco M4 with the latest firmware, set as AP mode, everything working fine until my router reboot, this Deco unit seems will take over the DHCP role once it found the main DHCP isn’t available, just like what Asus did, which is a good thing but it doesn’t restore unless I switch all Deco units off and on again.

 

It seems only occur when you have something connected on the LAN interface behind the Deco unit, I mean if I just plug in 1 LAN for Ethernet backhaul it’s ok, once I plug-in another LAN to connect eg. TV box, and the main router turned off, it will “intelligently” take over the DHCP role, and never go back.

 

As as an IT guy, I can confirm this is Deco’s problem, it shouldn’t have the DHCP Overriding function on, please tell your team to fix it by just turning it off, pretty simple, doesn’t take months to do it, right?

Hi,

 

The DHCP server will be disabled when it is turned into access point mode; while once the main router stops working (DHCP server is not available), in order to continue to manage the Deco unit, the Deco unit will turn on DHCP server temporarily so that the phone/pc can get IP address; while once the main router/main DHCP server back to work, the DHCP server will be disabled automatically. FYI, this function is called smart DHCP. When there is a DHCP server existed, the DHCP server of Deco will be disabled in AP mode, while once the main DHCP server stops working, it will be enabled automatically to keep the connection between the Deco and phones/pcs.

 

While if it never go back atfer it took over the DHCP role, please tell us the current network topology; and the IP address of PC/phones when Deco works as the DHCP server.

 

Good day. 

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#6
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Re:Re:Re:Re:Conflicting DHCP when Deco in AP mode ?
2019-04-27 09:59:38

Hello!

 

It's not working! Your smart DHCP is no functionnal.

 

I tried to disable my DHCP server and the DECO gave an adress to clients, but when DHCP returned on, the DECO still gave the adress to clients (seems to be the main deco adress as gateway)

 

Why it's not accessible for us to manage AP mode in manual mode, gave a static adress to the main DECO (and the slaves) and a gateway to main router to have a network to run like a charm instead of a poor automatic adressing that will not give perfect solution?

 

If it's possible, can you give all users the choice beetween manual mode and automatic mode?

 

Thanks

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#7
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Re:Re:Re:Re:Re:Conflicting DHCP when Deco in AP mode ?
2019-04-28 02:24:23

Hi,

 

Please kindly provide the below information regarding to your issue.

1. The IP address and default gateway obtained by your device when the DHCP server is available.

2. The IP address and default gateway obtained from the Deco unit when the DHCP server becomes unavailable.

3. The IP address and default gateway obtained AFTER the DHCP server back to work. 

Note: How to get them:https://www.tp-link.com/en/support/faq/838/

 

Besides, please try to reboot the main router and the Deco units after the DHCP server back to work and test whether the device obtains IP address from the original DHCP server.

 

Thanks in advance, and have a nice day. 

 

nobru26 wrote

Hello!

 

It's not working! Your smart DHCP is no functionnal.

 

I tried to disable my DHCP server and the DECO gave an adress to clients, but when DHCP returned on, the DECO still gave the adress to clients (seems to be the main deco adress as gateway)

 

Why it's not accessible for us to manage AP mode in manual mode, gave a static adress to the main DECO (and the slaves) and a gateway to main router to have a network to run like a charm instead of a poor automatic adressing that will not give perfect solution?

 

If it's possible, can you give all users the choice beetween manual mode and automatic mode?

 

Thanks

 

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#8
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Re:Re:Re:Re:Re:Re:Conflicting DHCP when Deco in AP mode ?
2019-05-10 14:16:45

@Kevin_Z ,

I don't know what it takes to TP-Link to acknoledge that the firmware has a problem when so many users are complaining.. I've been working with engineers on new mesh network hardware and had issues they couldn't reproduce in their labs.. well because they are labs and possibly aren't facing configurations/environments that come up in real-life.

 

Recently my Deco M5 was upgraded to 1.2.8 too, and I wish I could reverse that FW version back to 1.2.4.. I noticed this morning that my iPhone 6 couldn't get any IP address on the mesh WiFi.. though my other wireless devices seemed to be fine.

 

I had to login to my wired computer to check if my router had again started to play fool (like stated in my OP), but nope, according to the logs, it was rebooted 16 days ago.. so not the problem. I tried manual IP assignment on my iPhone, but that would be more or less a hit or miss. After finally rebooting my iPhone, I got a valid IP (not 169.xxx) and was able to connect to the internet.

 

What frustrates me is that the Deco App doesn't provide you any option to reboot the AP's when the whole setup is in 'AP Mode' !! how come ? big failure. Another point of frustration in the TP-Link HW, is that you cannot access the whole configuration over the local network with a browser ? why is this so difficult to put in place ?  Other Mesh Wi-Fi system offer both, a mobile app & browser login to manage your configuration.. What's so difficult to understand ?  I get it that TP-Link wants this system to be accessible to everyone, even the most Lambda home internet user, which probably doesn't have much IT knowlege, and the mobile app is Ok for that type of users, but don't block power-users that have enough IT knowledge to setup mulitple networks at home and even mix-and-match various HW to accomodate their needs..

 

This Deco M5 Mesh network is trully a powerfull HW for budget-savy people and works normally pretty well. But you could do a little more on the SW side and bring it from 'Great' to 'Fabulous' ! 

 

My current config goes like this : 

 

Cable Modem => ISP Router (Zyxel EMG-2926, Wifi disabled) => 8-ports TP-Link switch (wired computers) => Master Deco M5 (in AP Mode) => Wireless => Slave Deco M5 (2x)

 

The average network speed on Wi-Fi is about 135Mbps when doing the Internet speed test from the Mobile app, which is on par with what I'm supposed to get from the ISP. Internatl data transfer rate is around 300-350Mbps, which could probably be better, but considering the files were stored on an external drive, it's not the speediest channel. 

This is pretty good compared to other Mesh system I tested which weren't able to get to a third of this speed. 

 

I understand that it's "by Design" that the Deco in AP mode only offers reduced functionality, still sad that this little powerhouse can't be more flexible when it comes to management. And it would be nice to have access to some kind of system logs, which seems to be totally absent in AP mode (not sure if that is available in Router mode).

Thanks in advance for considering the feedback.

Have great day!

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Re:Re:Re:Re:Re:Re:Re:Conflicting DHCP when Deco in AP mode ?
2019-05-13 10:15:53

Hi,

 

Cause only the iPhone 6 cannot get valid IP address and can be fixed via reboot it; You can take some time to test whether it works. Any updates, just let us know.

 

Back to your inquiry, the Deco can be managed via Deco app only yet, while there is a plan to add web browser in the future, you can keep an eye on official website, any updates, we will post there. 

 

For other features missing under AP mode, we will remind our R&D colleagues and they can work on it and evaluate the feasibility.

 

Thanks in advance, and have a nice day. 

 

 

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