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
Deco M9 Plus in AP mode taking over DHCP server and assigning IPs in own subnet
2019-05-03 07:37:55
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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6 Replies
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. 

 

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#5
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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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