Reverse proxy header configuration warning from local network

Nextcloud version (eg, 18.0.2): 18.0.4
Operating system and version (eg, Ubuntu 20.04): Debian 10
Apache or nginx version (eg, Apache 2.4.25): Apache 2.4.38
PHP version (eg, 7.1): 7.3.14

The issue you are facing:
On the administration overview page I get the warning “reverse proxy header configuration wrong” (translated and cutted).
The strange behavior is, that the warning is only visible when I access my nextcloud instance from the local network. If I access the nextcloud administration page from my mobile phone using GSM there are no warning or errors :smiley:

Is this the first time you’ve seen this error? (Y/N): Y (Getting this error since I configured split brain DNS at home)

Configuration/ Topology:

  • Debian 10 running Apache and PHP with Nextcloud
  • Alpine 3.11 running traefik
  • Public DNS server
  • Private DNS server
  • Router

My public DNS server has an A record to my router’s IP. The router forwards traffic on ports 80/443 to my traefik instance. Traefik does the letsencrypt stuff and forwards the requst to my nextcloud instance. This works perfectly!
Now I introduced a private DNS server on my local network to avoid the routing through the public IP when I access my nextcloud instance from my home computer. So the private DNS server has an A record to my traefik instance.
When I access the administration page from my home computer (client IP is local 192.168.x.x) I get the warning.
When I access the administration page from my phone using GSM (client IP is public x.x.x.x) I have no errors or warning.

I know that is no critical error. But it is ugly :stuck_out_tongue:

Does anyone have an idea?


Hi all,

thanks to rubber ducking! I found the issue :smiley:

Of course I am using IPv6. And because I could not find a way to easy set static IPs, I used the fe80 link local address as static IP for my A record.
If I add the global IPv6 address with my IPv6 prefix to my hosts file the warning disappears :sweat_smile: