Cannot check http in private network

[afanjul]

Kuma Version

1.23.16

Describe the bug

Note: all IPs and domain names are invented.

I have a proxmox with containers. I'm using nginx proxy manager to reach that containers from outside (sharing the same public IP ex.: 172.125.25.25). Kuma is in a container with IP 10.0.0.100 and a wiki.example.com webpage is in a container with IP 10.0.0.200 and port 3000 (a nextjs project). Both webs are reachable from outside correctly. However, obviously, if I create a monitor for wiki.example.com, it doesn't work because the wiki.example.com resolves to the public IP.

So I've created a etc/hosts entry in the kuma container like this: "10.0.0.100 wiki.example.com", so now from kuma container command line I can do: curl -I wiki.example.com:3000 and it works perfect and responds with 200 OK.

root@kuma:/opt/uptime-kuma# curl -I http://wiki.example.com:3000
HTTP/1.1 200 OK
Vary: RSC, Next-Router-State-Tree, Next-Router-Prefetch, Next-Router-Segment-Prefetch, Accept-Encoding
x-nextjs-cache: HIT
x-nextjs-prerender: 1
x-nextjs-stale-time: 4294967294

However, if I set the monitor in Kuma like in the example screenshot, it doesn't works. I cannot debug the response so I cannot check why is failing, the event message is a "timeout exceeded":

Why is not working in Kuma application if i can do a curl to the same web and port from the same Kuma server?

To Reproduce

No response

Expected behavior

I expect that Kuma can validate the same check that I'm validating with a simple curl command from the same Kuma server.

Additional context (optional)

No response

[afanjul]

I have tried with another web page on port 80 (to remove the port variable) and it doesn't work either.
I have added a "ping" monitor to "wiki.example.com" and it does works, so it's a problem with the http monitor only.