Go to Network Center > Port forwarding > Port forwarding on your Synology Router.
For a Synology NAS behind the router, you may need multiple port forwarding rules because different services use different ports. Example from the knowledge base: forward public IP port 5001 to virtual IP 10.0.0.6 port 5001, then access DSM via https://210.61.203.200:5001.
If you are configuring it from DSM on a NAS, the older guides say:
- DSM 6.2: Control Panel > External Access > Router Configuration
- DSM 4.1 / DSM 4.0: Control Panel > Router Configuration or Main Menu > Control Panel > Router Configuration
The fragments do not include the full port list for each Synology service, only that you should open the ports used by the specific service. [1] [3] [11] [12]