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Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet

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Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet

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Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-05-03 07:37:55 - last edited 2023-02-23 09:57:07
Tags: #Feature Request #Access Point Mode #Highlighted Thread
Model: Deco M9 Plus  
Hardware Version:
Firmware Version: 1.2.6

After installing the M9 in access-mode in my network, I notice some devices cannot be reached anymore.

 

When examining the situation I notice that the IP the devices get is in the range the M9 uses when in router mode.
When switching to Router-mode, the (internal)M9 IP is: 192.168.78.1 and the DHCP range it uses is from 192.168.78.100 to 192.168.78.200 with a subnet of 255.255.255.0.
Router mode is unusable in my situation, so I'm forced to use the AP-mode.

 

Some devices (like a "Wemos D1" board, a Thermostat and sometimes my printer when turning it on) get an IP in the 192.168.78.x range while my
cable-modem (Lan Gateway with IP: 192.168.178.1 and subnet 255.255.255.0) is setup to handle the DHCP with a range of 192.168.178.30 - 192.168.178.250 .

 

The weird thing is that the cable-modem is UP all the time when one of these devices is added, but still doesn't get an IP from my Modem and because of the
different subnet, can't see the device. The device says it's up and running on the SSID from the Deco M9, with the Deco M9 given IP.
From within the Deco App, the device can be seen WITH the wrong IP address....
Because the devices it happened to are headless and no monitor can be attached, looking at the network from the device is not possible.

 

 

For some reason the Deco M9 DOES listen AND responds to DHCP requests in certain situations,
making networking a real challenge, even for someone with a good background in networking!

 

I hope someone will fix this serious flaw in the firmware...

I'm not the only one experiencing problems with DHCP in AP-Mode accordig to several other posters on the community.

 

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#1
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1 Accepted Solution
Re:Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet-Solution
2021-09-16 12:05:55 - last edited 2023-02-23 09:57:15

Update:

[Feature Request] Smart DHCP on/off switch under access point mode

It has been accepted and will be added in the future.

So far some models have added this feature already, while others will be added along with firmware upgrades. Please pay attention to the firmware release note on the official website.


 

And there seemed to be some misleading about "smart DHCP". This feature would not be enabled for no reason.

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 but to continue getting IP from Deco.

There are also cases that the "secondary DHCP server" in the network is something else:

A forgotten old switch was pushing out the 10.0.1.x addresses
An Apple Time Capsule assigned in the 10.0.x.x range

 

 

Please comment below if you have any further concerns.

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#123
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Re:Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-05-03 17:35:31

After attaching a serial-monitor to the Wemos D1 board it gave me the following output:

 

So the IP-Address(192.168.78.105) is in the Deco M9 Plus range instead of in that of the router and the GateWay address (192.168.78.1) is the internal address of the Deco M9.

 

 

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#2
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Re:Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-05-05 02:34:16

Hi,

 

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. 

 

Back  to your case, it is a little weird, the cable modem gateway is running all the time, while the devices obtained IP addresses from the Deco not the gateway. 

 

At that time, please try to power off the Deco units first and then check whether the devices obtain the valid IP address from the gateway; after that, you can power on the Deco and test whether they are working properly with the valid IP address.

 

Besides, please tell me the current network topology/diagram. 

 

Any updates, please let me know. 

 

Have a nice day. 

 

 

 

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#3
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Re:Re:Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-05-07 19:19:31

Yes, you are not the only who have this problem in AP mode, and TP-Link give us the same copy-paste answer!!!!!

 

 

I am really disappointed by the contructor who is using his "smart" DHCP that does not work! I have never seen an access point enabling DHCP when the router is not available! Devices who have received an IP then stay off the network!

 

TP-LINK solution restart the devices! a real shame !!!!!!!!!

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#4
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Re:Re:Re:Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-05-10 10:47:03

Hi @nobru26 ,

 

We are sorry for the inconvenience caused here, but we are trying our best to get more details to do further troubleshooting and try to fix it. 

 

Meanwhile, we have done a test at our lab already regarding to the smart DHCP when Deco M9 plus works as AP mode. 

 

According to the DHCP protocol, the PC will renew IP address in every half of the lease time, and the M9 will detect whether there is another DHCP server existed on the network; 

 

What we have verified is that the specific avoidance mechanism for smart DHCP feature set the lease time lower, which is 60 seconds, so that the client device cannot get valid IP address in time.

 

If you are willing to do further troubleshooting, you can provide the info mentioned above and then we can do further analysis. 

 

Good day. 

 

Nice to Meet You in Our TP-Link Community. Check Out the Latest Posts: Connect TP-Link Archer BE550 to Germany's DS-Lite (Dual Stack Lite) Internet via WAN Archer GE550 - BE9300 Tri-Band Wi-Fi 7 Gaming Router EasyMesh Is Available When Wi-Fi Routers Work in AP Mode as A Controller. Archer AX55V2 Supports WireGuard VPN, EasyMesh Ethernet Backhaul, IoT Network, Speed Limit,and More If you found a post or response helpful, please click Helpful (arrow pointing upward icon). If you are the author of a topic, remember to mark a helpful reply as the "Recommended Solution" (star icon) so that others can benefit from it.
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Re:Re:Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-05-19 20:53:58

Hi,

 

If you looked at the network diagram, you could see that if I disable the deco, no devices will get a DHCP-address from the gateway, because the WiFi devices can't access the network, because I use the Deco to create my WiFi network.....

 

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#6
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Re:Re:Re:Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-05-19 20:56:05

Oh and restarting the Deco's (I use 3 of them) is not something I'm able to do after a power outage when not at home.

If that happens, the devices get a faulty IP-address and stay unreachable, wrecking a lot of automated processes....

 

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#7
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Re:Re:Re:Re:Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-07-23 19:56:54

Agreed this is not desirable behaviour at all.

 

Disabling DHCP should mean exactly that. If you want a "smart" DHCP feature which will in most cases cause havoc with someone's network setup then also allow that to be disabled.

 

I've just had to go around resetting devices all over my house simple because my DHCP server was temporarily offline and all of a sudden my M9 units start throwing out DHCP leases to everything. Crazy setting!

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#8
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Re:Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-07-28 09:49:51

It's even so bad, that even when my main DHCP-server is up, the M9 devices take over the DHCP-request of devices broadcasting for a DHCP-server.....

Even when having the DHCP-setting in the M9 to OFF, you still have to use STATIC ip's for a lot of devices to prevent trouble.....

 

This is obviously a very big BUG and it needs to be sorted out... There needs to be an option to disable the DHCP of the M9 completely if you choose so, to prevent havoc on the network!

 

I've been a network admin of a network with 100k+ nodes and if you really wanted to get me mad you should try to put another dhcp server on the net....

Just.Bad.Design!

 

(Oh and if you didn't know by now..... I'm quite frustrated by the QA for a product this expensive......)

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#9
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Re:Re:Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-07-28 11:15:42
@Kevin_Z is it possible to provide a comment on what you intend to do about this feature considering the potential it has to cause serious issues on a network even when "disabled".
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#10
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Re:Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-09-09 23:24:14

I experience the same issue with M5 network.

 

I have a MOFI 4500 LTE router that provides NAT, DHCP (using the 192.168.10.0/24 network) and DNS and 4 M5s attached in setup in AP mode

 

If I reboot my MOFI router one of two things happen: 1. The devices keep their IP but start receiving the IP of the first M5 as their default gateway.  2. Just like others they start learning about the M5s router networks (when it was configured as a route) and get a 192.168.68.0/24 IP address.

 

My only cure is if I reboot the router to manually unplug the M5s around the house until the MOFI is back online.  Also related but not TP-Links issue is if there is another DHCP server on the network the router seems to not stay running.

 

Anyway, network is shown below:

 

 

Also, I've left my Airport Timecapsule enabled, because for some reason, I can't get my Epson 454 Workforce printer to connect the Deco M5s.

Blessings, Martin
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Helpful: 7

Views: 54693

Replies: 123

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Feature Request Access Point Mode Highlighted Thread
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