Subnet mask blank with Dynamic IP

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Subnet mask blank with Dynamic IP

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Subnet mask blank with Dynamic IP
Subnet mask blank with Dynamic IP
2019-09-16 11:47:30
Model: Deco P7  
Hardware Version: V7
Firmware Version: 1.3.1

After setting up my main Deco and connecting to my modem with dynamics IP, the Deco obtains a WAN IP address, gateway and DNS addresses succesfuly. However, the subnet mask is always empty. In this situation, none of my connected devices are able to browse and the Deco shows a solid red light.

As soon as I change to Static IP and enter a subnet mask (WAN) manually, it starts to browse and LED changes to green. I go back to Dynamic IP and it stops again.

Problem is that I cannot leave the config on Static IP as my ISP will always change IP of my modem and I also have not been able to figure out how to enter a subnet mask when dynamic IP is selected. Don't know why it always blank in dynamic IP either. Please help.

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#1
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11 Reply
Re:Subnet mask blank with Dynamic IP
2019-09-17 00:55:07

@dotman

 

With computer connected to the modem directly, please click here to verify whether it can obtain valid IP address, default gateway, DNS and subnet mask.

 

If it works properly, you can connect it to the Deco P7 directly and clone the MAC address. 

 

Besides, you can swap the locations of the Deco units to give it a go.

 

How to configure slave Deco as main Deco, please refer to https://www.tp-link.com/support/faq/2400/

 

May it help and have a good day. 

 

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#2
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Re:Subnet mask blank with Dynamic IP
2019-09-17 06:11:27

@Kevin_Z the clients have all the correct network settings, but still can't browse. It's the main Deco that's missing the subnet mask and hence nothing connected to it can browse unless I change it to static IP and enter the mask manually, which I don't want.

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#3
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Re:Subnet mask blank with Dynamic IP
2019-09-18 07:23:13

@dotman 

 

Have you ever tried to troubleshoot as the instructions mentioned above? 

 

Meanwhile, what is the model number of the modem? 

 

Try to hard reset the Deco P7 or swap the locations of the Deco to give it a go.

 

Besides, you can give ISP a call to verify is there any special settings at their end which may cause this issue. 

 

Good day. 

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#4
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Re:Subnet mask blank with Dynamic IP
2019-09-20 05:54:01
Hi @Kevin_Z Thanks for your reply. Yes I tried the instructions above without success. I think I figured out that the problem is that the modem tries to assign a mask of 255.255.255255 but the Deco is unable to accept this setting as I found out when I tried to enter it manually in the static IP setup. It will accept any other mask apart from this. This may be a flaw in the Deco firmware unless someone has a workaround. My laptop works perfectly when I connect directly to the modem with automatic IP (DHCP) setting by the way. It shows the mask setting of 255.255.255.255. My modem is Huawei LTE CPE E5172.
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#5
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Re:Subnet mask blank with Dynamic IP
2019-09-20 07:59:15

@dotman 

 

I'm afraid that you changed the subnet mask of LAN, not WAN. The LAN subnet mask cannot be 255.255.255.255. 

 

To do further analysis, please take a picture of the IPV4 page on the Deco app when it uses dynamic IP. 

 

In the meantime, try to assign a static IP and show us a screenshot as well. 

 

Besides, may I know who is your internet service provider? 

 

And please show us the current network diagram.

 

Thanks in advance.

 

Good day. 

 

 

 

 

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#6
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Re:Subnet mask blank with Dynamic IP
2019-09-20 12:28:42

I am afraid you are WRONG @Kevin_Z. I did change the subnet mask of the WAN. You should not assume that people must not know what they are doing simply because you have no solution to, or fully understand the problem. If it was the LAN subnet mask that was coming up blank, then how would the clients have been able to connect to the WiFi?

 

I agree that the LAN subnet mask cannot be 255.255.255.255. This is basic. The modem tries to assign the 255 mask to the Deco while in bridge mode with Dynamic IP selected. I confirmed this by connecting my laptop directly to the modem and checking the network settings. The only way the Deco works in this scenario is by switching to Static IP and manually setting the mask to anything other than 255.255.255.255.

 

Anyway, I found a solution to my problem by disabling bridge mode on the modem. Now the modem does not try to assign the public IP to the main Deco with a subnet mask of 255.255.255.255. The modem now NATs from public to private IP and Deco NATs the private IP to clients on a different subnet. Problem solved.

 

I guess I'll never know why the Deco is unable to accept the bridge mode mask of 255.255.255.255 which works well with my laptop and any other device connecting directly to the modem in bridge mode. Case closed.

 

Thank you.

 

 

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#7
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Re:Subnet mask blank with Dynamic IP
2019-09-25 08:36:39

@dotman 

 

When you change the connection type to static IP, you can change the subnet mask to 255.255.255.255, while what I said is that you cannot change the subnet mask when you use dynamic IP. 

 

Anyway, back to your case, you can provide the info/pictures asked on my last reply and then we can try to locate it and fix it.

 

Besides, you can try to clone the MAC address with computer connected to the Deco by wired cable.

 

Good day.

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#8
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Re:Subnet mask blank with Dynamic IP
2019-11-11 17:28:32 - last edited 2019-11-11 17:29:37

Hey @Kevin_Z  I'm having the same problem with Deco P7 and Huawei 4G modem in Bridge mode. Using Dynamic IP does not work because the Subnet mask is empty, changing to Static IP and filling subnet with 255.255.255.0 makes internet work but can't use static ip (as the ip will be  changed by isp).

 

My old router receives dynamic ip info correctly from the modem, and deco also works when connected to my old router. When I connect it straight to modem, dynamic IP gets all other info correctly exept subnet mask.

How to make deco simply fill subnet mask automaticly to fix this?

 

- firmware 1.3.1

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#9
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Re:Subnet mask blank with Dynamic IP
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#10
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Re:Subnet mask blank with Dynamic IP
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#11
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