In order to connect to the local resources behind a Synology VPN there is some additional configuration needed.
Let’s assume that you have already connected to the Synology VPN (see this link) and that your Synology NAS is at IP 192.168.1.100.
Open a terminal and type:
You should get something like this. Look for “ppp1”:
You then have to create a route to the Synology IP:
sudo route add -net 192.168.1.100/16 10.10.0.1
Where the first address is the IP of your Synology NAS and the second one is the IP of the ifconfig command.
Now you should be able to access all the resources in the subnet behind the Synology VPN.