Jellyfin Server can't be "discovered" - usual suspects?

[Iacov]

hey

my jellyfin server is in a "server vlan", separate from the media devices

when opening a jellyfin app (doesn't matter if android or amazon or google tv) there is no detected server selectable, i always have to enter it manually
some devices (which i trust more) are directly connected via IP and some other devices are connected via url (witch jellyfin being behind a nginx (proxy manager))
neither the IP nor the url ist being broadcast/discovered

i think that my media devices should be able to access jellyfin on all necessary ports
what are the "usual suspects"/user errors that cause a server to not be detectable on the lan?

[TheDreadPirate]

If it is on a separate VLAN and, I'm assuming, subnet then service discovery will not work. SSDP does not traverse subnets or VLANs without a router with the ability to modify TTLs. IIRC, the TTL on SSDP packets is 1. Meaning as soon as they hit the gateway to traverse to other subnets or VLANs they hit 0 and are dropped.