OK, so I don’t know what else to tell you. If it works, then leave it, I guess, as it is 
It’s possible your dynamic DNS provider had some issues.
Yea, it works from outside. now i will try to get it working from the inside again. i will try your tipps for that.
You simply need split brain DNS. I can’t tell you how to do it with Vodafone Routers. But thats the solution für the final problem now.
If you’re on Windows then you may be able to avoid setting up your own DNS by adding the server name and its local IP address to your hosts file. I’m not 100% sure if this still works in Windows 11 but I used to do that years back, before running my own DNS. I think Linux has a hosts file equivalent too. That would be the quickest solution, if it still works, as the OS should check the hosts file first, doing DNS lookup second.
Well the reason to use split brain DNS are not local network only devices like Desktop Computers. The reason are mobile devices, like notebooks, mobile phones and such.
If using NC-Client on mobile devices (eg Android, IOS) you want them to reach the NC-Server while in local WiFi and also while in external WiFi or 4G/5G networks. So the NC-Client must use in all cases the FQDN of the NC-Server (here http://mycloudr2d2.ddnss.de/).
If the mobile device is in LAN the LAN’s DNS need to resolve this FQDN to NC-Server local (private) IP-Address. If the mobile device outside the LAN any DNS used on it shall resolve it to NC-Servers external Ip-Addrsss. Otherwise you run into trouble.
Yes, of course, agreed. That’s why I run my own local DNS so my phones and tablets can use it too. I just presented another possible option and let danubis choose what works.
@adelaar @AdamAnon I thank you so much for your help.
I just did first what AdamAnon told me, and added a dns entry do the hosts file of windows.
I will setup as next project my own DNS Server. Idk how ressource intensive it is for my PI, together with my nextcloud. So I will test around.
I m still kinda confused why it isnt working from one to other day, like that my internal network coulndt find the dns name anymore. Thank you again for your help!
You’re welcome. I can’t tell you why it worked and now it stopped, but I know that this usually causes problems. So, your own, local DNS is the best solution.
Both AdGuard and PiHole can also work as DHCP servers so your devices will get your local DNS assigned automatically, both wired and WiFi. You’ll just need to disable the DHCP on your ISPs router. Otherwise, you’d need to configure DNS manually on all your devices.
It might sound daunting at first, but if you can set up your own Nextcloud then you won’t have any difficulties running either AdGuard or PiHole.
Both have similar requirements. I used to run AdGuard on Raspberry Pi 3 with 1GB of RAM and 100Mbps Ethernet. RAM usage depends on how many blacklists you have loaded and can vary from 300MB to over 1GB. I run it now on an old Dell Optiplex Micro, 3rd gen i3 with 4GB of RAM because I use some very big blacklists and 1GB was not enough for me. CPU requirements are minimal and RAM is the only consideration. DNS server is really lightweight.
I’ve ran AdGuard server for two years now and it has been 100% solid, zero issues, just run updates once in a while. I ran PiHole before, but they ruined the web UI few years back and I switched to AdGuard which has superior web UI, IMHO, that is. Functionally, both offer the same features and have similar requirements, just call some of them differently.
If you have any questions regarding AdGuard server then send me a PM and I’ll get back to you. But it’s really easy to install, set up and manage.
Good luck!
PS. If you just want a basic DNS, without the ad blocking feature overhead then Linux has native BIND DNS that is very robust, but I found it very difficult to set up and manage, it has no UI (unless you use Webmin or something) and I have no idea how resource heavy it is. But that’s one more option.
Thank you! I will prob. come back to it, if I will have some trouble about it.
It might be easier, to tell us brand and model of your router.
In that case it may be possible, that annother user can tell you, how to confiure your router, that calling your nextcloud from internal network will work.
That prevents you from manual network-settings on your computer and your mobile devices also will work from internal network as well as from outside.
It is a Vodafone Station 6. The problem is, that thing is very limited in options.
At the moment, I m trying to set up the DNS-Server on my Pi. I tried dnsmasq, but that didnt work out, because my phone and stuff didnt have connection outside of it, if I used my Pi as DNS-Server. I will try not Adam’s free solution first with PiHole, to get my phone and Wlan stuff connected in my network.
If you setup another DNS (e.g. the RPi) in your LAN this very limited Vodafone Station 6 must have at least the option do switsch off the DNS-Server build in the Vodafone Station 6 and offers the option to deliver via DHCP the iP-Address of the RPI as DNS-Server for the clients in your LAN.
You shall check that beforehand. If that options are not given you can’t solve the problems you face now that way without buy a new router.
Both PiHole and AdGuard have DHCP functionality. So, you disable the DHCP server built into the ISP’s router and use your own DHCP server instead.
That’s how I have to do this because my router does not have the option to change the DNS server, it always assigns the ISP’s own DNS server IP.
The only hiccup would be if danubis’s router won’t allow for its internal DHCP to be disabled. Then the DNS will have to be set manually for each and every device on the network, including smartphones, tablets, etc. This will work too, it’s just gonna be a pain in the butt.
So, either way, the problem can be solved without getting a new router.
Hello Guys, sry that it took so long to answer on that topic my solution. Didnt have time to test it out.
BUT finally, it works again. It was like you guys said, my router was blocking via rules which prob. got patched over night in, so i couldnt reach my cloud through my local network anymore.
I started with something lightweight as a DNS-Service, dnsmasq.
There I put my cloud as local adress and now it works. My devices are routing directly to my cloud, instead of trying first outside of my network and then going in, just to get blocked.
I used that tutorial for it.
Thank you again guys for helping me out here!