FAQ-Why Are VPN Tunneled Services Interrupted or Slowed Down When a VPN Tunnel Is Established by Using the L2TP over IPSec Dial-up Software of the Windows 7 Operating System

Publication Date:  2015-07-02 Views:  189 Downloads:  0
Issue Description
Why Are VPN Tunneled Services Interrupted or Slowed Down When a VPN Tunnel Is Established by Using the L2TP over IPSec Dial-up Software of the Windows 7 Operating System?
Solution
VPN tunnel-encapsulated packets from the firewall to the device with the Windows 7 operating system are fragmented. However, the VPN client of the Windows 7 operating system cannot decapsulate the fragmented packets. Therefore, the existence of large packets causes a service interruption or slowdown. You can change the MSS value on the firewall to prevent VPN tunnel-encapsulated TCP packets from being fragmented.

[USG]firewall  tcp-mss 1300                              
Warning: Configure tcp-mss will affect the system's normal service.  
Continue? [Y/N]:y 

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