Unable to use T-Mobile Home Internet with work VPN, any suggestions?

Hola Everyone, 

This is something I posted in another T-Mobile forum a while back. After putting some research into this, I believe I have found a solution (at least one that worked for me).

PLEASE NOTE: PART OF MY SOLUTION IS USING MY OWN WIRELESS ROUTER ATTACHED VIA ETHERNET CABLE TO THE BACK OF MY HOTSPOT MODEM. THE INSTRUCTIONS I LEFT BELOW WILL NOT BE OF MUCH USE TO YOU IF YOU ARE NOT USING A WIRELESS ROUTER.

This does not require much tech-savviness as I found what I needed from a YouTube video and a little googling on how to access the settings I needed, which I'll post a link to at the end of this. Basically, it's the MTU (Maximum Transmission Unit) settings that T-Mobile uses. You don't really have to know much about this other than how to find out how to change it, either on your computer or on your wireless router (if using a wireless connection). 

Most internet providers set their MTU size at 1500. This is more-or-less a standard most in the industry follow. From what I found, T-Mobile sets their MTU size at 1450. I'm not going to go into explanation on how this works; just know this is the problem. This tiny difference seems inconsequential, but can make or break your VPN connection. Unfortunately, it's on us as the customers to find our own solution(s) to this problem. 

This YouTube link gave me the information on how to check my MTU settings and change them on a Windows PC. This is a solution specifically for if you want to only change the MTU Size on individual PC's in your home. Ultimately, I did not change my MTU Size on my laptop, but the part of the video that helped me find the MTU Size was key to figuring this whole thing out. The link will take you directly a few seconds right before the spot you need to pay attention at begins:

 

I'm not a Mac user and am not experienced with using them, but this is a link for all y'all Apple fanatics that I found while I was searching for a reason for this problem. It was the first article I came across that set me on the path to figuring out how to change my MTU setting. Hope it helps:

https://amithkumarg.medium.com/resolved-t-mobile-home-internet-vpn-issue-2f5ca594c23e

And, lastly, I use a TP-Link Wireless router. This link is for TP-Link device owners and shows you how to change the MTU Size. There's no way I can find links to all the different types out there. However every brand's settings are easily searched on Google, so good hunting to you and good luck: 

https://www.tp-link.com/us/support/faq/1134/

I hope this helps some people. My issue is (self)resolved. 

This exact same thing happened to me out of nowhere today; I've had everything working flawlessly since I switched to tmobile over a month ago from xfinity and now it will not accept my work's vpn. I will cancel my service immediately if this cannot be fixed; this can cost me my job.

This is insanely frustrating. I can't do half my job unless I sit in a cafe with broadband access or work from a friend's house. But the part that is infuriating is every time I call T-Mobile, I get different answers from different people. Call 1: "Can't do anything for ya. Sorry." Call 2: "We can get you to a higher tier of support who will be able to help if you can get us your VPN Settings from your IT Department." Call 3: "None of what call 2 is true. Sorry to say it, but they lied to you. There is no higher tier of support."

I bet if I called a 4th time, I'd get another completely different answer. I had this totally fixed by changing the MTU size on my router and now, even changing it directly on my laptop makes NO difference. There really needs to be a fix for this. If I had access to any other ISP that wasn't worse than this, I'd drop this service instantly. Unfortunately, I'm stuck since I live in a rural area. I'll stop complaining now. 

I can't believe T-Mobile support just flat out told me that their internet service is incompatible with a VPN! How can they advertise that I can use this for work at home with multiple high speed streams, but just conveniently neglect to let me know I can't use a VPN! No suggestions for solutions, he just offered to cancel my service immediately!

My company uses Cisco AnyConnect VPN. I've been having all the same issues mentioned in this thread and gone down the IT rabbit hole trying to remedy this issue. Finally found a knowledgeable T-Mobile technician that explained if personal or work VPN or systems are operating on IPv4 then you need to go into your T-Mobile home internet app > select network > click "+" to add network > name network > create password > select 2.4 GHz band > select WPA/WPA2 > WPA "TKIP & AES" > then save the new network and connect. Worked out my VPN issues and my security cameras are working now.  

AJ1234 wrote:

[...] Worked out my VPN issues and my security cameras are working now.  

@AJ1234 My wife and I use company VPNs and they seemed to stop working the weekend of Jan 20, 2024. Is that when you started having problems?

My Ring cameras seemed to have stopped communicating with the mother ship, but Alexa appears to be up and running. I was already using the 2.4GHz band, but I didn't check the WPA settings. I'll try again next time I'm up there.

I'm in a rural area (Pine, AZ) and their aren't many options, so fixing this is critical for us to WFH. My VPN connected fine (more-or-less) to company resources, but I couldn't get to Google Drive. My wife's VPN had troubles using Teams and couldn't connect to a cloud app (website) she relies on.

Frustrating. 100% agree with @Homerthefox that it’s deceptive to market this as broadband alternative when so many people rely on WFH.

Wanted to post an update. Unfortunately, earlier today, my VPN issues returned. I have no idea what happened. I have tried everything I can think of and have even lowered my MTU size to the lowest setting and am still not able to connect to most apps while on my VPN. I apologize if you try my solution and it doesn't work for you. Was working perfectly at 1450 MTU until midday today. Hoping it's just an intermittent thing, but still wanted to post here. 

I was told as well they are working on it. I have perfect working Internet for everything but VPN for work. Any application that requires VPN (so basically all my work needs) won't stay working for more than 10 min. I have to reboot the computer, gateway, reconnect, and all that for 5-10 min. It's been like this most of the week but completely awful 1/24-1/26.

Really like this service and company, have phones with them and own stock in the company. If they cant fix this soon I'll have to rethink all that and go back to ATT, or worse Xfinity (barf). 

PLEASE DONT MAKE ME DO THAT………...PLEASE

Just to note on this thread in case anyone at T-Mobile is curious, I have GlobalConnect by Palo Alto Networks and this did NOT fix my issue at all.

Gfiz247 wrote:

AJ1234 wrote:

My company uses Cisco AnyConnect VPN. I've been having all the same issues mentioned in this thread and gone down the IT rabbit hole trying to remedy this issue. Finally found a knowledgeable T-Mobile technician that explained if personal or work VPN or systems are operating on IPv4 then you need to go into your T-Mobile home internet app > select network > click "+" to add network > name network > create password > select 2.4 GHz band > select WPA/WPA2 > WPA "TKIP & AES" > then save the new network and connect. Worked out my VPN issues and my security cameras are working now.  

THANK YOU!!! My company uses the same VPN and it worked perfectly until Monday, 1/22, probably the same change you experienced. I followed your guidance and it works perfectly. I'm back to the same full speed I had previously, maybe even faster, and now I have a second home network dedicated to work from home. 

Sadly, this fix lasted about 45 minutes. After that, and then after an hour on the phone with TM help desk it has been escalated.