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

Althius wrote:

I've recently been told by work Information Services that I cannot use my work laptop with T-Mobile Home Internet.   Here is there response to my support request.

 

T-Mobile's primary service called "5G Broadband" is not true wire-to-site broadband.  While Cisco AnyConnect can work over 5G and other wireless connections, MTS does not recommend its usage unless absolutely necessary, and if you utilize a phone line such as Cisco Jabber call quality cannot be guaranteed.

The issue is that while 5G can provide broadband level speeds and bandwidth wireless solutions, such as 5G, have a higher tolerance for "packet loss."  Packet loss is when individual pieces of data are dropped/lost during transmission.  For most applications this is a minimal issue that 5G speeds may render unnoticeable, but a live connection, such as the AnyConnect VPN or Voice Over IP phone services, will experience connection degradation or be completely disconnected forcing you to reconnect.

This is not an issue MTS can mitigate.  For this reason the only recommended Internet service types are fully wired based connections including DSL, Broadband, Cable, and Fiber Optic services.

 

Does anyone have a suggestion on a way to work around this issue?  It does not need to be perfect, but being able to work from home is essential, and if I can't use TMHI to do that… it would be a deal-breaker for me.

TheLostITGuy wrote:

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. 

¡GRACIAS! 

After troubling my company’s IT support for weeks, and them clean wiping my laptop and me getting everything set up all over again, I just realized that this is a t mobile issue. 

And this is the only solution thats working for me, an IPV4 connection did not help at all. 

The mtu that works best for me (my company's VPN settings) is 1370, and my Cisco VPN shows up as utun4, I have to change the mtu for this. And I need to do that everytime I connect to my vpn, which is fine, I have set up shortcuts to do that on my mac. 

But it is very clear, Google's speedtest didn't even load for me on VPN and even when it does sometimes, I barely got 5Mbps. After the fix its as good as outside VPN (120Mbps down). 

Couple of things, 

1. Tmobile is DEFINITELY to blame for this, I don't think its a "business decision" to "cut out all VPNs" like some have mentioned above, but someone messed up. The least they could do is allow us to change the MTU size, or to keep it simple, give an option "If your internet doesn't work with your VPN, check this box" and just use a low enough MTU size somewhere in their app. They've completely locked us out of any settings possible. 
2. The solution is not straightforward, it doesn't work if you just change the mtu for the default wifi, and not everyone can use a same number. You will have to try the steps mentioned (I referred to the medium post) and figure out what number works out best for your company's VPN. I'm guessing depending on the way its set up by your IT admins, even if its the same Cisco VPN, all of us have a different MTU that works best for us. 
3. If you can't do this yourself, get help from someone who would be able to understand and follow the medium article. The video just said "your interface name" which is wrong, I tried changing the setting for en0 (my default wifi interface) and it wouldn't work. The medium article explains it well. Also, depending on your OS and things you have installed, you could have more than just one interface. I guess using a separate router for work would be the best automatic solution, I'll try that soon.