# Android tablet DNS resolution error - router switch



## kunino (Jul 4, 2020)

I recently set up an old router as an ethernet switch (a BT Hub 5), and ever since have been having trouble connecting an android tablet to the internet.
I keep getting DNS resolution errors or "Your connection is not secure" errors with Chrome and Firefox, and other apps just refuse to connect at all.

All my other devices have no problems connecting, both wired and wireless. If I turn off the BT Hub then the tablet connects properly straight away, so the problem is obviously some sort of conflict created between the two, but I am at a loss as to what, exactly the problem is, and how to fix it (short of ditching the Hub).
I have already turned off DCHP on the Hub, and have turned it off on the tablet, too. The static IP address is not shared by any other device. I have tried changing the DNS servers to the Google ones. Nothing works. Sometimes it does connect briefly, but it always reverts to DNS errors before long. So, any insight into how I can resolve this?


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## zebanovich (Mar 2, 2019)

if on all devices DHCP is off, then all devices are set to use static IP and custom DNS?

Is time up to date on android tablet?


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## kunino (Jul 4, 2020)

Time is up to date, yes.
DHCP is still on on the main router, set to a range that does not overlap with any of the static IPs.
BT hub (the switch router) is set to static IP different from the main router, as is the tablet. The tablet is set to a custom DNS (tried the default router one and the Google ones, no difference).


I actually had a similar DNS resolution problem with my main PC when I first set up the second router as a switch. 
The problem was fixed by turned off IPv6 in the PCs network settings. Unfortunately, you can't do that on Android devices.


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## zebanovich (Mar 2, 2019)

> T hub (the switch router) is set to static IP different from the main router, as is the tablet.


First make sure tablet is on the same subnet, has same subnet mask, and valid IP that fits into subnet range.
DNS server doesn't matter much if this is properly set.

Then if that doesn't work you can try resetting tablet network
https://www.wikihow.com/Reset-Network-Settings-on-Android


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## kunino (Jul 4, 2020)

Subnet, subnet mask and IP are all set correctly.

Just tried resetting network settings. No help.


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## kunino (Jul 4, 2020)

The weirdest thing is that these DNS/security errors are delayed.
As I said above, if I turn off (or disconnect) the BT Hub, I can connect to my main router with the tablet no problem. 
If I then turn the BT Hub back on, the tablet remains connected and I can continue browsing or using any other apps which need an internet connection.
But, if I then turn the tablet off, when I turn it back on again things have reverted to DNS errors in the browsers and no connection for other apps.


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## zebanovich (Mar 2, 2019)

If I'm not wrong these issues can be resolved with routing, adding a route to table.

Not sure how to do this on android OS, sorry.


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## kunino (Jul 4, 2020)

I don't know how to do that, either.

Unless some other people can think of a solution, I may have to fall back on my plan B: ditch the BT Hub from the network and the buy a long Cat5e RJ11 cable so that I can move my proper router upstairs.


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## TerryNet (Mar 23, 2005)

Exactly how is the BT Hub 5 connected and configured?


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## kunino (Jul 4, 2020)

Ethernet cable from the main router to the Hub (connected to LAN ports, not WAN). Then two devices are connected to the Hub via ethernet, and two wirelessly. All work fine.
DHCP is turned off on the Hub, set to fixed IP address, different from any other device on the network.

I must (broadly speaking, at least) have things set up and configured correctly as if I didn't then surely I wouldn't have everything else working?


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## TerryNet (Mar 23, 2005)

I agree with your above post. Apparently the tablet has trouble when it connects to the hub instead of the main router.

What is different? You said some things earlier that hints to me that the tablet may connect to the hub's 5 GHz band but the router's 2.4 GHz.

Or is it used at a location where there is interference (e.g., from a neighbor's wireless network) with the hub's Wi-Fi but not with the router's Wi-Fi?


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## kunino (Jul 4, 2020)

The main router is 2.4Ghz only. The BT Hub has 2.4 and 5Ghz bands.
But I've tried all sorts of combinations. 
I've tried connected the tablet to the main router's wifi (but with the Hub on and connected). 
I've tried connecting it to the Hub's wifi. 
I've tried turning off just the 2.4Ghz band on the Hub and connecting to it with just the 5Ghz band active.
I've tried turning off just the 5Ghz band on the Hub and connecting to it with just the 2.4Ghz band active.
I've even tried turning off the wifi on the BT Hub completely (which obviously isn't a long-term solution, as I want it as a wifi extender), and even that doesn't work.
Nothing works.

The only thing which works is turning off or disconnecting the Hub wholesale. In other words, it seems just having the Hub on the network at all causes problems for some reason, no matter how I try to configure the wifi.


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## TerryNet (Mar 23, 2005)

kunino said:


> I've even tried turning off the wifi on the BT Hub completely (which obviously isn't a long-term solution, as I want it as a wifi extender), and even that doesn't work.


With the hub's Wi-Fi off I can think of only two ways that the hub could trash the tablet's connection.

a. When you made this test you had not yet turned off the hub's Dhcp and had not yet assigned a static address to the tablet.

b. IP conflict between the hub and tablet (pretty sure you have been ultra careful to avoid this possibility).


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## kunino (Jul 4, 2020)

Just tested again with the Hub wifi completely turned off.
Hub IP adress is set to end .2
Tablet is set to end .40
Main router's DHCP range is 50-250, so no conflict there, either.

Still DNS errors in browsers and no connection in apps.

I tried reseting my network settings on the tablet then connecting again to the main router (BT Hub wifi still off through all this). I had a working connection for all of about 5 seconds, and got onto a couple web pages, then it errored again and remained so.


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## TerryNet (Mar 23, 2005)

I have nothing else to offer. There have been cases of a particular wireless adapter and a particular wireless router just not playing nice together (change either one and you get a connection), but this is the first instance I've run across of a wireless device and an ethernet only (the hub with the Wi-Fi off) device not playing nice together. Makes no sense to me.


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## kunino (Jul 4, 2020)

Oh well, thanks for trying, at least.
I guess buying a long Cat5e RJ11 cable it is.


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## kunino (Jul 4, 2020)

Just tried an old tablet I had kicking around, and it connects and works fine. It's a different make, and running an older version of Android (4, whereas the Huawei I'm trying to use is running 5), so I guess the problem must lie either with the hardware or with something in the settings of Android 5.

As I mentioned before, I had similar DNS issues with my main PC initially, and they were resolved by disabling IPv6 in the network settings, so I have a feeling the issue with this tablet may well have to do with IPv6 somehow, too. 
How to fix it, though, is another issue, as I cannot alter the IPv6 settings of the tablet, and cannot disable it in the BT Hub.


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## TerryNet (Mar 23, 2005)

kunino said:


> As I mentioned before, I had similar DNS issues with my main PC initially, and they were resolved by disabling IPv6 in the network settings, so I have a feeling the issue with this tablet may well have to do with IPv6 somehow, too.


Excellent point. That does seem to be what you have isolated to.


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## Couriant (Mar 26, 2002)

Just out of interest, the date/time for the tablet is correct?


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