No remote access to Plex Server on Synology NAS - double Nat situation

[dor_isch]

Server Version#: 1.17.0.1709

Hello together,
I am trying to access my plex server from outside of my local network, but i have no success so far. situation:
plex running on synology nas
nas has no dhcp running, just get an IP from my fritzbox 6490 cable.
portforward from fritzbox to nas is set

if i refresh the remote access setting on the plex server, it shows up for 2-3sek as fully available until I get a double nat situation.

my problem now, is to figure out, what creates the double nat. each result or post i get ends up with a second router or something similar, but i am currently not aware which divice could do that.

network
fritzbox - wlan
-nas on lan1
- dlan on lan 2
- pc and tv on dlan

there is a section on the router, where i can see the whole mesh, including the dlan and with device is connected with it. each device is in the same ip range 192.168.178.xxx , cant find a second one. but there should be at least a second one, when i understood double nat correct.

i am glad about each tip.
Kevin

[dor_isch]

Hi trumpy,
Thanks for fast respond. But its exactly the problem. Everyone mention a second router and/or second subnet.
I dont have a second router. Each device have same subnet. So there is no device to switch into bridge mode or something. Have no clue where i should continue.

[dor_isch]

Plexserver told me that. As mentioned in my first post. If i refresh the manual port in the serversettings it works for a few seconds. After that the double nat is coming up.
Yes i read your post and faq q22 too, but there is no solution for me, or i am not able to extract it from that post. I did the whole setup like portforwarding ect, but i cant set a router to bridge mode, cuz i have only one.

[dor_isch]

I probably found it.
I have only ipv4 ds-lite-tunnel, that seems to create the trouble. and as far as i know, plex dont fully support ipv6.
seems like no solution in the moment for me