AVM uses provider's DNS despite setting another one in its interface

[fraternl]

I would like to share my experience of a Fritzbox that stopped working properly after migrating to another provider without any changes to its config.
In the end it was all due to the provider's DNS not answering to their network it was on.

The way that AVM handles this situation isn't that elegant, IMHO.
In AVM I can "override" the nameservers in the Internet account settings.

This "overriding" is however merely partial.
In /tmp/avm-resolv.conf it has the provider's DNS servers and it persists in using those (DNS-servers) for dyndns, ntp and telephony
I thought I could get it all to work again by putting this in /tmp/avm-resolv.conf and restarting the voip daemon, but alas, to no avail

cat /tmp/avm-resolv.conf

nameserver 8.8.8.8
nameserver 8.8.4.4

voipd -s
voipd

My guess is that they are merely sourced from there and are copied somewhere else (bad behaviour IMHO)
I was able to get telephony to work in that situation (bad provider DNS) by changing the voip's proxy to the Voip provider's IP.

The provider has now changed the configuration of their DNS-server, so everything is now working without all that patching.

I am however somewhat disappointed on AVM's total dependence of the DNS-server that's provided by the provider with DHCP or PPP.
I may have good reasons not to use their services for DNS.
I sure had until they fixed their config.

I also suspect that AVM uses the system time it gets from DSL.
When I didn't have 8.8.x.x addresses configured in the Fritzbox and the provider's DNS was not working I had Januari 1970 in my Freetz environment.
In the logs of AVM I had the correct time. It couldn't have had that time using IP's NTP as DNS was not working at the time. I suspect it came from DSL, but it could also have been from the other fallback mechanism.

Maybe this is supposed to be common knowledge to you, but I sure wasn't aware of this behaviour and this is after 20 years of using Fritzboxes and 15 years of Freetz.

[fda77]

AVM uses still the same suspect mechanis since 20 years...
To understand dns you could use

• showdsldstat
• route -n

and you see AVM sets a NETWORK ROUTE to the configured DNS servers !!!?!?!?!?
In the closed-source daemons of AVM this is then handled somehow on routing...
Additional, you should NOT USE another local DNS Server, eg Fritzbox 192.168.178.1 and your "Raspberry server" is at 192.168.178.111.
If you the use this Tasperry, it could be used as DNS, but there is then NO OTHER COMMUNICATION with this rasperry (if i remember correctly this IP thenhas also no internet access...)! Eg if its additional a mail server, the fritzbox could not send notification mail with this Raspverry...

To hack around this crap, you could use multiple IPs for you local server
Or set the DNS of fritbox to 127.1.2.3 where a dnsmasq runs which can "normal" use another device for upstream-dns

Because of many of such bad things AVM does not add common things like VLAN or multiple SSIDs

[rcourtman]

This is tracked in #732 (PBS Temperature Collection). The sensor-proxy architecture that collects temps on PVE hosts could work on PBS hosts, but there's no integration yet.