TOT Tplink td854w wifi modem router assigns wrong IP address?

[WorriedNoodle]

Hi Guys,

Not sure if anyone can point me in right direction to fix this myself?

We have a TOT Tplink td854w wifi modem router and a number of Android, Win10 and a Samsung Smart TV devices accessing it via wifi.

* With our Android devices sometimes we can connect to the wifi but not the internet. I notice using an app such as Network Signal Info that the app reports cannot get external IP. I also notice it has listed the device local IP something like 192.168.1.103 which is already the same IP number used by another Android device connected. How is this happening when each device should have its own IP? It only seems to be an issue on Android devices as the Win10 and Smart TV are always connecting to the internet OK.

Can someone help explain what is happening please? Is it the router (set up as provided by TOT) or some fault with Android - devices using Kitkat versions mostly?

[RichCor]

As you've discovered, IP addresses should not be duplicated on the same LAN.

This sometimes happens when you assign 'static' IP Addresses to devices that also are being issues by the Router's DHCP Server subroutine to 'visiting' devices.

Duplication can also happen when the Router's DHCP Server subroutine issues out an IP address (under temporary time-based lease), but the device that accepted it doesn't recognize the 'lease' limit and continues using it after the lease expires, and DHCP re-issues the IP address to another client.

So, make sure any 'static' IP addressed you manually enter into any devices are outside of the Router's DHCP Pool (reserve of IP address range for temporary/dynamic devices).

If you have device that don't 'travel' to other networks, you might consider issuing them 'static' IP address manually.

Also, make sure you only have one device issuing DHCP addressed (some people 'repurpose' additional WiFi Routers to extend WiFi coverage and forget to disable the unneeded/conflicting router features).

[WorriedNoodle]

So, make sure any 'static' IP addressed you manually enter into any devices are outside of the Router's DHCP Pool (reserve of IP address range for temporary/dynamic devices).

Thanks so much for your very helpful answer. I finally looked at my Android devices and as you pointed out it seems they were set to Static IP in the wifi settings of each device. I have since changed them each to DHCP and now the problem seems to have sorted itself out. Some devices are a bit slow getting external IP, but they do eventually.

* On your point above how does one the range of the routers DHCP Pool? I suppose it should be by accessing the router menu using 192.168.1.1 but I cannot seem to find that info? Maybe I need to look again?

Anyway many thanks.

[RichCor]

Yes, the router DHCP IP address pool is set in WebConfig on your router.

Should be under Interface Setup / Internet, or Interface Setup / LAN

DHCP

DHCP Server

Starting IP Address:

IP Pool Count:

Lease Time:

Edited September 28, 2015 by RichCor

[WorriedNoodle]

Thanks for the Pool info. I will check this tonight when I get back to the router.

* I have since found the source of my problem and why it is related to Android only. I have been using various Android apps to change the DNS 1 & 2 settings to that of my choice. It seems that when I fix DNS to my choice in Android (I tried various apps such as Wifi Settings and DNS Changer) the IP address changes from DHCP to Static always without option to change this back to DHCP? If I choice DHCP again through the Android o/s interface the DNS settings I previously set get removed, which I don't want.

** In Windows it appears possible to have automatically selected IP address and fixed DNS. Is there a way in Android to do this - preferably with an app?

[RichCor]

According to a HowToGeek article,

Android and iOS devices allow you to set a custom DNS server, but this will only apply to a single network. In other words, you can change the DNS server for your home network, but you’ll have to change it again each time you connect to a new Wi-Fi network.

So, works just as you've observed. Not very convenient.

If you have a preferred set of DNS Servers you prefer for ALL of the devices connected to your Internet then this is easily done by setting the preference on the Router webconfig setting. But if one or more devices need a different set of DNS from that used by all the rest for special apps to function then they need to be set manually. Just know that if these are portable devices that, as stated above, the device will need to be retweaked back to DHCP when you want to connect to a new WiFi network.

Otherwise it seems you'll need to do a manual configuration of those special purpose devices and assign each a unique non-duplicate STATIC IP address that's not used as part of the DHCP address Pool.

[WorriedNoodle]

Very useful replies thanks. It reassuring to know I am generally on the right track.

During this thread I have since found is that I no longer need to change the DNS on my devices and can use default as my main app that required it ( Kodi with BBC iPlayer latest addon update) now works without DNS change.