Hey i have been trying to setup the SRP527W to allow VPN access ether via PPTP or L2TP/IPSEC to a Wiindows server!
short story! the old ADSL Router Died and looked for a more reliable one purchased SRP527W configured ports to forward to Server
4500, 1701, 1723, 500 and 433
I enabled the VPN Passthrough for L2TP, IPSEC and PPTP
i know about the GRE Tunnel unsure if its setup Correctly
Tunnel Number: 1
Tunnel Name: Workplace
Enable: Yes
Checksum: none
Sequence: none
Key: None
key Value: N/A
Wan interface Name: PVCO
Destination IP or Hostname: 192.168.XXX.XXX
Remote IP Address/Subnet Mask: 10.0.0.0/8,172.168.0.0/16, 192.168.0.0/24