VPN (SonicWall) will not connect over T-mobile 5G Hotspot

I found a post about turning off IPv6 on my WiFi connection on my Windows laptop that resolved this issue for me.

The issue I was having was that from my Windows laptop, I was NOT able to VPN into my workplace using my personal hot-spot thru my iphone 12 (I’m running iOS 15.1.1) using TMOBILE.

To resolve the issue, I had to disable IPv6 on my Wireless connection on my laptop.

Do disable IPv6 on my Wireless connection on my Windows laptop I did these steps:

1. Open “Network and Internet Settings”
2. Under “Advanced Network Settings”, Click on “Change adapter options”
3. It will bring up a list of Network connections, double click on the one that says “Wi-Fi”
4. In the new dialog box, click on “Properties” bottom left, do NOT click on “Wireless Properties”
5. The next dialog box will have a list of "This connection uses the following items”
6. Scroll down in that list to find “Internet Protocol Version 6 (TCP/IPv6)”, this will be in the list after the “Internet Protocol Version 4 (TCP/IPv4)”.
7. Uncheck the box in front of "Internet Protocol Version 6 (TCP/IPv6)". Leave the IPv4 checked.
8. Hit “OK”

After I did these steps I was able to use the VPN client (in my case it is the FortiClient VPN) and I was able to successfully VPN thru my hot-spot thru my TMOBILE service.

I also went back and retested using a normal WiFi connection (thru my home network) and everything still worked in that case too.

I have had the same problem with my Samsung A32 5G for the last 3 months, giving up. All devices connected to its Hotspot go to "connected without internet" any time after connection, rendering Hotspot virtually useless. Two more warranty replacement units failed in the same way.  The same A32 of my wife's works fine though, even VPN connection too.  Oneplus N200 5G and older Samsung J7 Star work flawlessly.  5G related? What is going on, T Mobile?  I have been left in the lurch with your nonchalance.

Experiencing the same issue receiving numerous calls from our employees working from home using T-mobile's new 5g home internet.  My IPSEC VPN (Global Protect) will not work over the other T-mobile hotspots either. Spent half the day with Sonicwall's engineering to find T-mobile's service was not passing the VPN traffic on ports 500 & 4500.  Hot spots on Verizon and ATT work with no issues. 

I'm experiencing the exact same issue with my Samsung A32 5G. Just activated this phone last Friday and tried to connect to my work VPN over the hotspot and it's just left to "Connecting". I tried troubleshooting based on internet suggestions to change the mobile network away from 5G so either (a) LTE/3G/2G or (b) LTE/3G but experienced the same issue. I moved the SIM card to my previous Oneplus 6T and it is working. That is my current workaround but this is seriously an issue that T-Mobile needs to look into and fix. So now I have to carry 2 phones just in case I need to work and access my work file network.

Today (5/22/21), I was advised by tier 2 technical support that T-mobile does not support the use of VPNs through a cell phone hot spot.  This was in response to my issue of not being able to establish an IKEv2 VPN from my laptop through the hot spot on a Samsung S20G FE.   (I can do so using a different ISP without issue).   When I asked for the document that stated as much, it was not immediately available.  I was told I would have a copy within 72 hours.   I am not holding my breath.

I can establish an SSL-based VPN connection through the hotspot, probably because SSL has to be supported for an internet connection to be of any value whatsoever.

I consider this a material failure since T-mobile does not make this information available when one signs up.  I am considering legal action to negate the contract.

bhorn wrote:

I don't known if this will help but  I could not use my tmo samsung s20+ 5g phone as a Hotspot to VPN into office from a laptop.  The solution was to change the properties of the wifi Hotspot device on my laptop to unchecked ipv6 and everything worked fine.

It's something worth trying, but it did not help me.   The core issue is that T-mobile does not support VPNs through a cell phone hotspot - as they have told me.   SSL-based VPNs do work, not because T-mobile goes out its way to support them but because SSL is so pervasive a hotspot that did not allow it would be all but useless.

In my case, I am trying to use an IKEv2-based VPN - which is native to Windows - but requires a bit of effort on the part of the carrier to allow the necessary ports and protocols to be opened/allowed.  T-mobile is apparently unable or unwilling to make this effort. 

I have the same problem.  I think it has to do with T-Mobile using ipv6 instead of ipv4.  Any suggestions on a work around?

T-Mobile using ipv6 instead of ipv4.

Keep in mind that, at least for me, the WatchGuard SSL VPN (based on OpenVPN) works just fine with the phone’s hot spot and I know the firewalls at the other end are not using IPv6 (I manage them…. :)).   

Find out for sure whether your VPN is SSL-based or IPSEC/IKEv2-based.   If the former, there may be something you can do, but if it's the latter, you may be out of luck.   

Both types of VPN work just fine when I use my regular ISP (Cox Cable).

Hopefully this helps someone else.  I had this same problem with my s21 5g phone.  I saw a suggestion to switch to 3G.  Poof.  I immediately connected to my work VPN.  I was then able to switch my phone back to 5G and stay connected.  The next time I tried I left it on 5G and it worked.  I don't know the technical reason, but it seemed like it somehow couldn't pass the VPN security while on 5G, but after connecting once, it's all good.  Maybe someone else can explain better, but worked for me. 

BenF12345 wrote:

Hopefully this helps someone else.  I had this same problem with my s21 5g phone.  I saw a suggestion to switch to 3G.  Poof.  I immediately connected to my work VPN.  I was then able to switch my phone back to 5G and stay connected.  The next time I tried I left it on 5G and it worked.  I don't know the technical reason, but it seemed like it somehow couldn't pass the VPN security while on 5G, but after connecting once, it's all good.  Maybe someone else can explain better, but worked for me. 

Thank you for the information.   Please clarify whether you were making the VPN connection from your phone itself or if you were making a VPN connection from your laptop and using the phone as a hotspot.   Also, do you know what type of VPN you are using (SSL, IPSEC, IKEv2, etc.)?

At least some of the folks in this thread are trying to do the latter (connecting from a laptop)