Over Christmas, my awesome wife bought me a Synology DS214 for my expanded home lab. One of the many reasons Synology was selected is because the DSM operating system supports multiple VLANs. However, the web interface only lets you set one interface. I found a number of conflicted articles describing how to configure the other VLANs. I upgraded my Synology to DSM v4.3 and then followed the process below to add the VLAN setup.
Depending on your switch setup, you may need to remove all VLAN configuration from the Synology’s port until the VLAN is created, or you can tag a single VLAN, or you can tag multiple VLANs and set a native VLAN. In a worst case scenario, you can connect the Synology to a port with no VLANs, configure the first VLAN, then move it to a properly configured tag. I trust the reader to understand and troubleshoot their local network configuration. If you do lose all connection to your Synology, you can always reset it to defaults and try again.
UPDATE: This process is confirmed to work with both DSM v4 and DSM v5!
UPDATE TWO: This will not work with DSM v6! See the comments for details.