TP-Link Deco BE85 BE22000 Tri-Band 10G / 2.5G Whole Home 3-Piece Mesh System - Manual (Page 69)

66 * Features available in Deco may vary by model and software version. Deco availability may also vary by region or ISP.
(11) Select Use preshared key for authentication and enter the IPSec
Pre-Shared Key you have set for the L2TP/IPSec VPN server on your
router. Then click OK.
(12) Switch to the Security tab, select Layer 2 Tunneling Protocol with
IPsec (L2TP/IPSec) and click Advanced settings.
Done! Click Connect to start VPN connection.