Technical Tip: Increasing the stability of L2TP

[Anonymous]

Description	This article describes the ways in which FortiGate administrators can reduce disconnections on L2TP VPN environments.
Scope	FortiOS 6.2.4+, 6.4.0+, 7.0 & 7.2.
Solution	To configure L2TP over a FortiGate firewall, it is recommended to consult the following article: https://community.fortinet.com/t5/FortiGate/How-to-configure-L2TP-over-IPSec-on-a-FortiGate/ta-p/197... In some situations, the network environments between the final L2TP users and FortiGate are negatively affected by out-of-order packets. Out-of-order packets can cause malfunctions in the L2TP negotiation processes, which can be viewed in debug logs through the CLI: diagnose debug application l2tp -1 diagnose debug console timestamp enable diagnose debug enable ipcp: down ppp:0x7fc426052000 caller:0x17762110 tun:-1  <--- LCP Termiate_Request id(6) len(23)                      <--- Use the following CLI command to improve the stability of L2TP in certain scenarios: config vpn l2tp set compress enable | disable*   <-- Enables/Disables data compression. The default is 'disable'. end