Help T-Mobile Issue - Cannot Resolve Host Names On Mobile Network

[Jon Wilder]

Hi all. New to the forum.

I switched to T-Mobile a few months ago and found what appears to be a limitation on their network. I use my phone to access my home alarm panel and my security cameras as well as my home intercom system no matter where I'm at. Because my home ISP provides a dynamic IP address, I have a host name registered with Dyn-DNS that points to my home network and my Dyn-DNS information entered into my router's DDNS client.

I use an app supplied by Bosch to access my alarm panel. This app uses my DDNS host name to access it on my home network. Prior to switching to T-Mobile, I was on Verizon and did not have this issue with them. My first T-Mobile phone was an LG Optimus L90, which had this issue. I figured perhaps upgrading to a Galaxy S5 that this would rectify the issue, but nonetheless I'm still having the issue even with the S5.

When I am on a WiFi connection, everything works as it should. However, when on the T-Mobile network, it cannot resolve the host name. If I use the outside IP address of my home network instead of the host name, I can access it no matter where I am whether I'm on WiFi or the T-Mobile network.

It appears that unlike other cell providers, T-Mobile's network/DNS servers cannot resolve host names. Does anyone else have this sort of issue? Does anyone happen to know why this is? Is there any way to force the phone to point to a DNS server other than T-Mobile's DNS servers when on the T-Mobile network?

 

[Crashdamage]

This is really a question for T-Mobile tech support. Dial 611 and they should be able to help. Of course, like with any tech support these days, you'll probably have to go through answering the usual scripted questions before getting transferred to Level 2 tech and the kind of help you'll need. But I've found T-Mobile's more advanced tech people to be good.

IDK how T-Mobile will resolve this. Of course they have DNS servers that can resolve hostnames. I've had T-Mobile service almost 18 years and no problems. DNS problems can be tricky. A fix can be as simple as deleting some cache files. Just a gut feeling has me thinking IPV6 is involved your case. But the upside is that at least you can make it work by using the IP address instead of the hostname.

 

[kate]

Hi Jon, welcome to the site!

I moved your thread to the T-Mobile forum

 

[EarlyMon]

Let's see if DNS or routing is the issue.

Check out "Ping & DNS"

https://play.google.com/store/apps/details?id=com.ulfdittmer.android.ping

I believe that your device ought to be on something like YOURS.dyndns.org yeah?

So in the tool above -

Enter dyndns.org

Get on to T-Mobile

Try Ping - IPV4

If successful, try Traceroute

If successful, maybe dyndns.org isn't updating your final address, most likely a configuration problem I suppose.

You can try the above with your device if dyndns.org Traceroute works - I don't expect everything to respond to a ping.

Repeat all of the above through your wifi - did you ever leave your home network and come back in or was the route known to be in-house and it never left?

You may also need to check your router firewall - it could be blocking outside access.

If you want to send me your device name, I'll check a Traceroute from my side but let's leave that for last because you don't know me (even though everyone else does).

If you can get on another wifi network to see for yourself, a relative or friend, even better from a personal security point of view.

Keep me posted, hope this helps.

 

[Jon Wilder]

Let's see if DNS or routing is the issue.

Check out "Ping & DNS"

https://play.google.com/store/apps/details?id=com.ulfdittmer.android.ping

I believe that your device ought to be on something like YOURS.dyndns.org yeah?

So in the tool above -

Enter dyndns.org

Get on to T-Mobile

Try Ping - IPV4

If successful, try Traceroute

If successful, maybe dyndns.org isn't updating your final address, most likely a configuration problem I suppose.

You can try the above with your device if dyndns.org Traceroute works - I don't expect everything to respond to a ping.

Repeat all of the above through your wifi - did you ever leave your home network and come back in or was the route known to be in-house and it never left?

You may also need to check your router firewall - it could be blocking outside access.

If you want to send me your device name, I'll check a Traceroute from my side but let's leave that for last because you don't know me (even though everyone else does).

If you can get on another wifi network to see for yourself, a relative or friend, even better from a personal security point of view.

Keep me posted, hope this helps.

Thank you for your reply. As per your post, I downloaded Ping & DNS from the play store and did both a ping as well as traceroute. Both were successful on 4G as well as WiFi.

 

[EarlyMon]

Thank you for your reply. As per your post, I downloaded Ping & DNS from the play store and did both a ping as well as traceroute. Both were successful on 4G as well as WiFi.

So dyndns and T-Mobile sound righteous - my next guess would possibly be your router or its firewall not letting that in from the outside.

 

[Jon Wilder]

Normally I would agree. However, I am able to connect just fine using the host name from ANY WiFi network. As long as I have WiFi access, it works no matter where I'm at. Just not on the cellular network.

 

[EarlyMon]

Normally I would agree. However, I am able to connect just fine using the host name from ANY WiFi network. As long as I have WiFi access, it works no matter where I'm at. Just not on the cellular network.

Can you traceroute down to same end node (e.g., your panel) ip address from both 4G and wifi?

 

[Jon Wilder]

Can you traceroute down to same end node (e.g., your panel) ip address from both 4G and wifi?

Yes I can on both WiFi and 4G.

 

[EarlyMon]

I just can't see any fault with T-Mobile here.

Let me think out loud.

They resolved the address correctly and have a verified signal path all the way to the end point.

I can't see the Bosch app shaping the messages the messages any differently.

OK.

Check your APN settings - make sure that you don't have a proxy set up.

Traceroute uses ICMP - Internet control message protocol - not something that you'd normally use in any other kind of app.

So an ICMP message could bypass a proxy where a web message would not.

And an APN proxy would not be in effect for wifi.

 

[Jon Wilder]

I did check my APN settings, which were set up by default. No proxy set.

However, on Saturday I did put a call into T-Mobile regarding this issue. The guy got back to me stating that some T-Mobile customers had a similar issue connecting to certain email servers on 4G as well. He had me create a new APN identical to the default one, but had me set the APN Protocol on the new one to IPv4/IPv6 (the default is hard locked to IPv6 only).

Ever since I created and switched to the new APN and restarted the phone, we finally got the app to connect to my panel on 4G. I'm gonna test it over the next few weeks to ensure that and everything else continues to work and no new issues arise.

 

[Crashdamage]

I figured it would be worthwhile to contact T-Mobile tech support. They're really pretty good once you get past the script readers to the backroom guys.

I thought this problem somehow was related to T-Mobile going all IPV6, and legacy support for IPV4, DNS64, etc by 464XLAT. Or something to do with all that. I did a little research and tried a couple of tests with HE Network Tools. But I couldn't put it together in my head so that I felt I could add anything intelligent to the discussion. I did find some info that covered creating a new APN with IPV4/IPV6 and I should have posted it for you.

Anyway, I still can't really explain it. I feel like my initial gut feeling about the cause of the problem has been justified, but I'm just not enough of a network guru to explain the whole thing in a coherent way.

Oh, well...you got it working and that's what counts.