cannot download files from SMB share on windows 2019 server over VPN

Enchy\ 1 Reputation point
2022-05-18T00:51:07.857+00:00

Hello, i got problems with downloading files on Win server 2019 over VPN L2tp, smb share works fine over LAN
Windows server got 2 network interfaces WAN (external ip from provider) and LAN, firewall profile is domain for both - firewall disabled for testing, vpn server i use to connect also running on this machine and also i installed wins server to make server accessible with netbios name

My client is Windows 10 machine, after connecting to VPN, i can ping server by its IP or hostname or domain name its okay, i can even browse files on its smb share and upload files with good speed but when i try to open or download even txt file, speed drops to 0 and everything begins to lag even crashing explorer.exe but if wait very long time file finally opens

This server also connected to another VPN and it can access smb shares from that network, but users from that remote network has same problem with downloading files.
As server has external ip i can access my shares directly without VPN '\external-ip\share\' if i do so - no problem with downloading files from smb share, but i want to use share over vpn

Please help me, what is the reason of this strange behavior?

Windows Server
Windows Server
A family of Microsoft server operating systems that support enterprise-level management, data storage, applications, and communications.
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  1. Limitless Technology 39,351 Reputation points
    2022-05-24T07:14:27.227+00:00

    Hello

    Thank you for your question and reaching out. I can understand you are having issues related to downloading SMB files over VPN.

    Please note that its expected behavior while downloading Files Over VPN and VPN should be used to access Servers and Company portals.

    In your case Disable any Antivirus program or Windows firewall you may have for temporary purpose.

    There are few network settings which you can consider.

    1. Reduce the MTU size on the VPN endpoints. A lot of devices default to 1500. You can try setting this to 1400 or 1350.
    2. Adjust the TCP Maximum Segment Size to something around 1400 has been reported to work.
    3. Check the resource utilization on the network devices involved. Routers and firewalls are computers too, albeit very specialized computers. If resources become overtaxed, this will cause problems. Some manufacturers, like Fortinet, build code into the OS that throttles services when resource utilization is at higher levels.
    4. Check to ensure the VPN is passing traffic correctly and not dropping packets
    5. Try a different protocol (e.g. FTP) to see if the bottleneck is SMB or the VPN.

    --If the reply is helpful, please Upvote and Accept as answer--

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