Isolated VPN server behind a router?

Question

VPN

Essence of the question: There
is a router with a pptp server running on it and a LAN behind it There
is also a machine on linux as a PBX (Asterisk) in the same LAN
There are also geographically remote voip backgrounds with vpn support machine with Asterisk so that VOIP phones connect directly to Asterisk via L2TP via an external static-ip (so as not to shine port 5060 and encrypt traffic) and the PPTP server also works for rare access to the LAN from outside for wheelbarrows. those. 1 vpn pptp is required on the router and l2tp isolated from the locale on the machine behind the router at the same time. How to implement all this in order to feng shui?

Answer 1

forward the port for l2tp to the machine with Asterisk
configure the firewall to prohibit packet forwarding from the l2tp network virtual interface