@d0ugmac1 

Hey!

The Fritzbox previously ran as a modem and router. Telephony was possible without restrictions. After setting up the Omada things, it worked at first and then telephony was no longer possible. I restarted Omada router and 200, like Fritzbox and then it worked again. A Grandstream WLan phone has the same problems as the Fritzbox. I just remembered that I still have a Raspberry in the DNS and use Homeassistant and Adguard to pull out the adverts. So the Adguard is the DNS server. But that didn't cause any pain before and doesn't provide any obvious reason. Would still have to be tested (remove and restart everything). Thank you very much for your help. I tend to be travelling with dangerous half-knowledge ;)

Frank

  @Liftboy 

A Grandstream WLan phone has the same problems as the Fritzbox.

The Grandstream does have the ability to send a SIP debug log to a syslog server I believe.

As said earlier, I suspect its down to tracing the SIP traffic with Wireshark. You could probably use the port mirroring on the ER707 to mirror the WAN port and thus see exactly what's happening

I have heard from the DSL/telephone provider that VoIP telephony must run via the DSL connection.

There is certainly a routing option here ... .

At the moment I have the DSL connection on the Fritzbox and only use it to run the telephone. I need to find some more time to deal with it and understand it.

Thanks for your help so far!

Frank

  @Liftboy 

I found this comment on another froum

If the FritzBox units that Zen ship are working in the same way as an ISP a bunch of my German users are using is, then it's probably not going to work.

It isn't just that the FritzBox needs to have a working internet connection, it needs to have a public WAN IP address or the SIP services don't start at least that's our theory. One of my guys had a play about to see if he could get it working with the FritzBox being behind another NAT router but gave up in the end.

  @MisterW 

I also fear something like this. If necessary, move the phone numbers to a SIP provider.

Thank you very much for this tip! I'll get in touch with the ISP O2 ;) and report back.

Frank

  @d0ugmac1 

I had already done exactly that and was very surprised that it was not successful. Over the holidays I will test how it looks when only the DSL is connected to the router and the Fritzbox with DMZ goes over the DSL WAN port. Today I opened a case with the ISP, but nowadays it's also a game of chance to get someone who can't just read from a piece of paper ';)