OpenWRT and PPTP VPN

PPTP uses the GRE (Generic Routing Encapsulation) protocol to create a point-to-point tunnel. As a pure IP protocol, GRE uses only IP addresses, but without the port numbers given by a router with NAT, and without the delay in establishing a connection. In its basic configuration, OpenWrt Backfire is capable of one PPTP connection when NATed, but not multiple such connections simultaneously. It is also unreliable when trying to set up successive single PPTP connections from different LAN clients in rapid succession. This limitation can be lifted (I felt so far) by installing the following package: kmod-nf-nathelper-extra