VPN issues

Like many others I had to change my MTU settings to stabilize my work's VPN.  There are many posts where people said what MTU setting worked for them.  After trial and error I found that 1480 worked best for my companies VPN.  I recommend searching "TMobile MTU VPN" to see what the others said.  Additionally I disabled IPV6 just to be safe.

Here is the process that I used:

Windows 10 > Search > CMD > Command Prompt (run as administrator)

This command shows you your current MTU settings on your pc/laptop:  “netsh interface ipv4 show subinterfaces”

This command changes your MTU setting:  “netsh interface ipv4 set interface "Ethernet 2" mtu=1480”

Replace “Ethernet 2” with your Interface connection.

VPN: ProtonVPN & using the desktop app. Internet: T-Mobile Home Internet Gateway: Fast 5688W
So I just spent the last few hours troubleshooting this problem, and was able to solve the problem.
Before I replied on this post I spent an hour or so of searching forums and protons site, and followed the recommendation of trying each protocol (within Protons Desktop App, has to be a paid account to make a custom profile and set which protocol to use) to determine if one was faster then the other (Smart, Wireguard, OpenVPN(TCP), OpenVPN(UDP)
Nothing made a difference. I could connect to some sites like Proton.me but 90% of most sites timed out including those that I use to help diagnose the network like "https://ipleak.net".
"https://packetlosstest.com/" y "https://www.speedtest.net/" would connect to the site but always fail when testing the speed or packet loss.

I started by resetting the default settings and clearing the cache/cookies in Brave, Opera & Edge.Still all the browsers had the same problem & timed out connecting to most sites.
I made sure each browser and ProtonVPN had firewall exceptions, before completely shutting off my firewall and windows defender.
Tried resetting the ip and flushing the dns from Windows Command Console before completely resetting my network and restarting the computer.

I still had the same problem, so I started researching my isp, T-Mobile Home Internet. I noticed in a few posts that T-Mobile doesn't fully support Ipv6, so I went to my network adapter settings and turned Ipv6 off. Then I turned ProtonVPN's protocol to OpenVPN(TCP).
This was the first time I was able to fully connect everywhere with decent speeds.
Out of curiousity I then went and turned Ipv6 back on, Everything continued to work fine.
So I am not sure why when I tried OpenVPN(TCP) in the very beginning it didn't work, why it works now after toggling Ipv6 on and off. Maybe because I did a network reset then set ProtonVPN to OpenVPN(TCP)? Im not sure. Its working now though.

I also saw in the same forum numerous people were having good luck with reducing their MTU to increase their speeds. "https://homenetworkgeek.com/mtu-size/#How_to_Access_Command_Prompt_in_Windows"
"https://amithkumarg.medium.com/resolved-t-mobile-home-internet-vpn-issue-2f5ca594c23e" (If you can't read the article because your not a member goto bing, search for 'resolved-t-mobile-home-internet-vpn-issue-2f5ca594c23e' and when you find the result goto the cached version of it. Then while veiwing the cached version disable all scripts for the page and reload. You should have the full article)
My speeds before I changed the MTU were ping-76 down-16.03 up-3.66
Testing from the same location afterwords ping-60 down-24.76 up-5.19
I only tested it briefly but it did seem to make a difference

I would have provided a much simpler reply if I had been able to pinpoint what exactly fixed my problems. So I figured it was best I just wrote everything down :))

ddv

trying to figure out if i used an actual vpn router if it would make internet speeds faster right now my vpn works perfect installed on my fire stick, computer, tablet and cell phone i was thinking of adding express vpn aircove it is a wifi6 router its supposed to increase your mbs by a minimum of 1200mbs and can connect to multiple vpns at the same time i just wanna make sure it will work with my tmobile wireless router i have now and if it is actually capable of doing what it says anyone have anything to add that will help me out or have ever used express vpn router before i use the vpn through the website with the software download right now and it seems to work great especially on my fire stick i have been able to access out of market shows and games that i couldnt before.

hello there.  I have Ipvanish VPN and it works great with this VPN.  I have no problem with connecting to the Internet.  And if you have a bad connection try moving it around the house until you get a good signal.  I was getting good for my signal then I moved it around the house on the second floor and found a corner in my bedroom that gave it an excellent signal so I got a cornerself and mounted it up high where I got that excellent signal and put the gateway on the self . And now I have Excellent service and connection. So try doing that and see if you can find a Hotspot like mine . Remember look all over your house till you find it 👌🏾👌🏾👌🏾😁

Hola All,

FYI - I debugged VPN internet issue with Tmobile technical team. They mentioned that T mobile dont work well with VPN as they keep changing IP address. 

So no point to keep discussing this issue as T mobile technical team agreed and not seen positive response/effort to fix it. Better to switch back to other internet provider. T mobile is not made for VPN users. 

I couldn't connect to my IP cameras inside my house due to the lack of a fixed IP address, however, I came up with a workaround that allowed me to see the camera images.  That is, I placed all the camera images onto a spare computer screen, and connected that computer to my cell phone in the field using "Any Desk"; a desktop sharing application.  In other words, I tunneled (?) through the T-Mobile hotspot.  This was a kluge, but it worked.  However, hooking up the rest of the house would be a nightmare, so I'm sticking with my current ISP. (Note: any desk sharing application can be an outright security threat. )

alvarorb wrote:

I read somewhere that turning off IPV6 could solve the issue. ...

Thank you! Yes disable IPv6 from your computer's network connection(s). For example, if you have Windows 10 and use WiFi then right-click the wireless connection > Open Network & Internet settings > Change adapter options > Right-click on the network connection you use > Properties > Uncheck Internet Protocol Version 6 (TCP/IPv6) > OK > Restart your computer.

J57little wrote:

All devices and home network are good. Signal strength is 2 bars (weak, but functional).  Spouse needs to set up VPN to work from home, but even IT from the office could not get VPN to work via T-Mobile Home Internet.  VPN worked just fine on the same computer using cable network. 

My company tech’s told me to check the box in the Cisco AnyConnect Settings     

Check   Allow local (LAN) acccess when using VPN (if configured)  

It now works.