ATT LTE hotspot periodically keeps disconnection laptop VPN

Greetings @dhilipvenkatesh!

The default value for NETGEAR routers, adapters, and switches is 1500 MTU. However, there's most likely a port on your CISCO device that needs to be enabled to allow traffic. We recommend AT&T ConnecTech. They're available at 1-866-294-3464 during the hours of 8 am – 11 pm Central Time, 7 days a week and can be billed to your credit card account or your home billing telephone number.

We hope this info helps!

Lar, AT&T Community Specialist

Hi,

How can I find out if port is being blocked? The behavior that I am seeing is that VPN connects fine, but every 10 second or so keeps reconnecting. When it does reconnect I see the below error from cisco diag logs. 

In this case the client is the ATT wifi hostspot that I am connecting to.

Description: TUNNELPROTOCOLDPDMGR_ERROR_INCORRECT_TUNNEL_MTU:The client detected via the DPD mechanism that the current tunnel MTU was incorrect.

Hello @dhilipvenkatesh

Are you using the a Hotspot feature, or a standalone mobile Hotspot device? I

Kenneth, AT&T Community specialist

Using the hotspot feature on my mobile device and sharing my existing data plan

Thank you @dhilipvenkatesh. We would like to continue in private so we are sending a PM. Please reply to the PM from ATTCares located in your Forums inbox so we can get started.

Kenneth, AT&T Community Specialist

Greetings,

We are experiencing this exact same issue.  Can you please advise of the fix that worked for @dhilipvenkatesh ?

Thanks!

I have not found a solution for this yet. Working with ATT team on the same.

I am impacted by this everyday as I am remote most times and I cannot use my hotspot to work. 

Hi dhilipvenkatesh,

From our investigation, it appears as if something has changed within the AT&T network.  As a workaround, we lowered the MTU setting that we have configured on our ASAs for the remote access VPN connections.  We tried a bunch of different MTU values, and we found that an MTU of 1320 works for us.  Our original MTU was 1350.

I hope this helps you with your issue.

I have not got a lot of help from AT&T mobility, connectech and every other team I called. Issue is that even after sending AT&T the entire diagnostic logs they are unable to find out where the problem is and I keep hearing hotspot is fine. My biggest frustration is not knowing who to talk to to get this fixed. I hoped that a company of this size, who cares about customers will take care of customers needs but in this case I feel helpless. I keep hearing from support that if use VPN they cannot help, does that mean that AT&T will not support any customers who have VPN issues? I do agree that there may be a problem with VPN client itself but the same VPN client works with every other mobile hotspot provider (T-mobile, Verizon, Sprint etc) so I am not sure why only AT&T has issues with VPN provider. Any help from the community is greatly appreciated as I am not getting the right technical details from AT&T. 

I am a network engineer myself so I need to be able to talk to an engineer in AT&T to explain the problem I am facing, but I was told there is no way to talk to a technical engineer. I am still hoping that I can find a solution to this simple problem so I don't have to switch providers. 

Exact same issue and no one seems to be able to fix.  Works fine on Verizon network so clearly an AT&T hotspot issue.  Do I need to switch networks for can AT&T figure out why it works on their competitors and not them?