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

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. 

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).

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?

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 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.

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.

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.