The Synology NAS is not a VPN server so you tell it to connect to your VPN Server which unclear to me what VPN Server you have elected to use.
More at https://www.synology.com/en-us/knowledgebase/DSM/help/DSM/AdminCenter/connection_network_vpnclient
Stumped. First attempt setting up a VPN. I've configured the VPN on my Synology NAS, forwarded the necessary ports, etc. I'm able to connect successfully from my Android phone, so I'm pretty confident the server side is right. On the Win 8.1 machine, I have defined the AssumeUDPEncapsulationContextOnSendRule = 2 in the registry, I've set the recommended IKE and IPSec services to automatic, I've turned off IPv6 in the VPN connection configuration. I've also confirmed l2tp passthru is configured on the client-side router. Anyone seen anything else? Help