So if I understand this right you will need to change the network on the port attached to the synology in your UniFi configuration or set the vlan tag in the synology OS, I would do the former.
doesn't the switch terminate any VLAN tagging at the port? so if I add the VLAN to the DSM configuration it doesn't receive any tagged packages and refuses them?
It sounds like you just added a second network/vlan to the existing interface which means you actually created a trunk and are getting the old network untagged and the new network with vlan tags which the synology is dropping.
with all the other devices in the IoT subnet it works with setting the VLAN on the port of the switch. If I check back on the unifi site, I found this:
'Applying a VLAN to a Switch Port
Native VLAN
The Native VLAN is the VLAN assigned to "untagged" traffic passing through a switch port. Devices physically connected to a switch port will be placed on this Native VLAN.
Tagged Networks and Trunk Ports
Ports can be configured to allow traffic from other networks. Allowing specific networks/VLANs is referred to as “tagging” them on the switch port. You can see all ports’ VLAN tags in the VLAN Viewer, found in the Ports tab.
Ports that have been tagged to allow traffic from multiple VLANs are referred to as “trunk” ports. By default, all ports on UniFi Switches are trunked to allow all VLANs. '
if I understand that in combination with your comment correctly: I set the native VLAN to 83
so everything tagged with 83
is correctly forwarded to the NAS and accepted there, stuff tagged with 1
are non native, the tag stays on and the NAS doesn't accept it?
But that would make the Synology NAS quite hard to use in any corporate setting with multiple VLANs which need to interconnect
and why does it work the other way around? while being in the default net 1
it does accept stuff from VLAN 83
Synology OS also doesn’t really support trunked ports through the UI (even though it does support a port that only uses a vlan tag) so it’s much easier to just leave them untagged.
which would mean, I can't put it in the IoT net?
I changed the native vlan to '83' and allowed all others
The isoöation is done with firewall rules blocking access from the IoT net to default, with some exceptions (dns, media nas (currently), etc.)