VPN issues

Not sure if someone found out how to correct the issue already. Changed my settings, the VPN protocol from UDP to TCP protocol.  It works fine now

I was getting a situation with the VPN where it appeared to connect, but it was not functional.  The problem is the MTU packet size value.

For me, I found lowering the MTU value at the client fixed the problem.  The tmobile(nokia) modem seems to be set to 1450 and the cable company was set to 1500.  I don't think Tmobile will change it at their end. The built in Windows 10 VPN client defaults it to 1400, but there is some header information that moved it past the 1450 window.

1. Find the interface-With the VPN “connected”, initiate the administrator command prompt and type netsh int ipv4 show subinterface.  This will give you a list of interfaces like this:  

      MTU  MediaSenseState   Bytes In  Bytes Out  Interface

   ------  ---------------  ---------  ---------  -------------

     1400                1    2073205    1650218  MY VPN

   4294967295                1          0     167019  Loopback Pseudo-Interface 1

     1500                1  384370968   39338930  Wi-Fi

     1500                5          0          0  Bluetooth Network Connection

     1500                5          0          0  Local Area Connection* 1

     1500                5          0          0  Local Area Connection* 2

     1500                1          0     311118  VirtualBox Host-Only Network

2. Then, back down the MTU setting with netsh int ipv4 set subinterface “MY VPN” mtu=1380 store=persistent.  You may need to adjust the 1380 value lower for your system.  

3. exit the VPN and then restart the VPN and see if it works.

4. If you want to dig deeper, you can figure out when the MTU value craps out with ping www.yahoo.com -f -l -1500 and keep lowering the "1500" value until you see "Packet needs to be fragmented but DF set".  The last value that worked is close to what the modem is set to.  I'd subtract 70 from that value and set the client mtu to that.

Josh123 wrote:

I have read that T-MOBILE is sharing IPv4 addresses.

what the heck. Is this common in the wireless industry?

I've had the gray Nokia Gateway since signing up in April and it worked great with my work VPN until that router died and I set up the new one today.  I can still connect to VPN, but am unable to connect to my soft phone server. It's the same model router as the old one and nothing else changed.  I can connect to the soft phone if I use my hotspot.  Anyone ran into issues like that?

rogerbock wrote:

I was able to solve my VPN issues using the guidance in https://amithkumarg.medium.com/resolved-t-mobile-home-internet-vpn-issue-2f5ca594c23e.  This was on a MacBook + Cisco AnyConnect.  I don't think I needed to change all of them, but I set the MTU on four network adapters to 1350:

en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1350
utun0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1350
utun1: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1350
utun2: flags=80d1<UP,POINTOPOINT,RUNNING,NOARP,MULTICAST> mtu 1350

Assuming this is something that can be fixed at the router level, I really hope T-Mobile pays attention to this thread.  Not every user is going to be tech savvy enough to do this on their own.

I would be one of those 'Non Tech Savvy' people that this exact problem is effecting. :( If not I'll be off work for weeks with no other internet options in my area to work from home.  I hope TMobile reads these feeds and is able to help.

I'm extremely disappointed that T-Mobile does not publish a list of incompatible VPN devices. This country is working from home, many with VPN devices. I have been on several long waits and calls only to find out T-Mobile does not support the Cisco Meraki VPN. My company's IT team has had similar issues with other carriers but resolved it with getting a static IP Address assigned. This is not an option from T-Mobile. My company will now inform new employees which carriers to use, I guess some will be blacklisted. What are the chances T-Mobile will notify me IF this problem is resolved before I return to my ISP that just buried fiber in my street? Aside from this, the 5G home router works excellent for all my other connected devices.

I switched to T-Mobile home internet couple days ago and I realized that my and my spouse's VPNs did not work. I called Tmobile and they updated the firmware and my Global Protect Network worked then, but my spouse's Cysco VPN did not work at all and they said they would give us a call back within 24 hours but never got a call back yet, in 48 hours. My Global protect does not work anymore either and I have to sign in to work tomorrow. I live in an area where there are many t-mobile service towers, I think. And I have been using their wireless for years and am happy with their wireless service. I'm not sure if I can afford the time to keep calling tmobile and be on a  2-hour call with a t-mobile technician. I'm planning to go back to my old service provider. I would have appreciated if t-mobile was transparent upfront and let their customers know they there might be VPN issues. I'm unhappy with the tmobile home internet service!

rogerbock wrote:

I was able to solve my VPN issues using the guidance in https://amithkumarg.medium.com/resolved-t-mobile-home-internet-vpn-issue-2f5ca594c23e.

This fixed the problem for me, too. Thanks. I'm on MacOS + GlobalProtect VPN.

Paso 1

On Windows 10, launch Command Prompt as Administrator 

Paso 2 

Run this command and get the name of the interface you are connected to. Mine was "Wi-Fi"

netsh interface ipv4 show subinterface

Paso 3: 

If MTU is 1500 or more, reduce it to 1400 or lower 

netsh interface ipv4 set subinterface "Wi-Fi" mtu=1400 store=persistent

Paso 4:

Verify if MTU is changed 

Paso 5:

Reconnect your VPN and try going to pages or applications that had problem earlier. Works like magic. Try lower MTU, maybe 1350 if issues persist. 

I am having the same issue. while accessing a website of my friend. His website basis on hair dryer products. is this a website or vpn?