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i have a raspberry pi with multiple services running (e.g. Openhab, mosquitto, ...). each service should be locally reachable via a local subdomain (openhab.core.local, mosquitto.core.local, ...)

Of course, there seems to be a simple solution - mDNS. But here comes the problem: enter image description here

Here we the the mDNS discovery. The service, port and local IP are recognised correctly. Everything goes on the right network client to port 80 where an nginx (also tried Traefik) reverse proxy container awaits for requests to route. But I cannot reach the services.

I've figured out that the DNS Rebind protection in the FritzBox will not answer DNS questions which resolves to the internal network, ok. Ive configured the exceptions for the desired domain names. (also tried with several subdomains different configs) Where I do not quite understand why it needs an DNS server response if we already have the mDNS entry, but ok. enter image description here

Nothing changed.

So the client knows that home.pink-core.local should go to 10.0.0.40:80 where the nginx waits. The services are up and running. But the client seems to makes an DNS request with no resolution despite of whitelisting in fritzbox. At least the services are not reachable.

How to figure out the reason and resolve this?

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  • mDNS and DNS are two very different protocols.
    – Rui F Ribeiro
    Commented Mar 7, 2021 at 6:30
  • Yes, I know. That’s why I was confused with the fritz box „solution“. IMHO it should be enough to publish the service via mDNS and every device in the local network should be able to resolve to this services. Regardingless of any DNS FRITZ!box blocking.
    – Peter C. Glade
    Commented Mar 7, 2021 at 9:04
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    Fritzbox does not talk mDNS. If you are trying to feed mDNS into a DNS .local domain, you will run into issues. See also my answer in this thread unix.stackexchange.com/questions/457166/… ; I would advise forgetting mDNS and using proper DNS, especially for office use.
    – Rui F Ribeiro
    Commented Mar 7, 2021 at 11:34
  • I had already feared something like this. Interesting that the FritzBox so against this technology locks it is quite a recognized technique? Or are there better alternatives for simple local network service publishing?
    – Peter C. Glade
    Commented Mar 7, 2021 at 21:57

1 Answer 1

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mDNS uses a local Link Multicast IP Adresse (IPv4: 224.0.0.251, IPv6: ff02::fb, UDP-Port 5353) with TTL fixed to 1, so not to be routed. You need a mDNS proxy annoucing the service and the target IP Adresses of the appliances.

A Raspberry Pi or OrangePi Zero can do; instructions can be found here(sorry, only in German)

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