On 2025-05-10 04:26, Ondřej Surý wrote:
> I think there's too many moving parts.
>
> Personally, I would suggest to remove systemd-resolved as a first step
> and configure the system to use the configured resolver directly.
>
> Systemd-resolved was disabled a while ago. One of the first things I
> did.
>
> However, it is also unclear to me whether the desktop station in
> question is Linux, Windows and if it is Linux what distribution does it
> use.
>
> I have both. Mostly, I'm using a Windows 7 desktop (the one I'm on
> right now) to do testing. I also have two Windows 10 laptops. There is
> also one Ubuntu client (22.04, same as the server).
>
> As I said - too many moving parts and it's not even clear where to
> start the debugging.
>
> I appreciate your help, nonetheless. I will try to stabilize things to
> make the parts "less moving." I will focus upon eliminating any
> remnants of Systemd-resolved first and then take it from there.
>
> Ondrej
>
> -- Ondřej Surý -- ISC (He/Him)
>
> My working hours and your working hours may be different. Please do not
> feel obligated to reply outside your normal working hours.
>
>> On 10. 5. 2025, at 9:03, Greg Choules via bind-users
>> <[email protected]> wrote:
>
> @Danilo you are correct, the contents of /etc/resolv.conf are not set
> by BIND and BIND itself does not use them. But all applications running
> on that machine (including dig, unless you specify @<address>) that
> want some kind of name resolution will make OS system calls and then
> the OS *will* use what's in resolv.conf to determine where to send DNS
> queries on behalf of the application.
>
> In the very first mail, bind9 said that the BIND config contains this:
>
> listen-on port 53 { 123.123.123.10; 127.0.0.1; };
> At startup, the named process will tell the OS to send it packets that
> have those destination addresses AND destination port 53. All fine so
> far.
>
> However, bind9 also said this:
>
> The resolv.conf file contains:
>
> nameserver 127.0.0.53 Confining things to the Ubuntu box for now, this
> tells the OS to make DNS queries to 127.0.0.53 - the 53 is *not* the
> port number, it is the 4th octet of the IPV4 address.
> So the OS sends queries to 127.0.0.53 and named is listening on
> 127.0.0.1. I think you can see that this isn't going to work.
> I don't know why resolv.conf contains that nameserver address (and it
> is an address, not a name - read the man page for resolv.conf), but the
> easiest solution would be to add that address to the set that named is
> listening on. i.e.
>
> listen-on port 53 { 123.123.123.10; 127.0.0.1; 127.0.0.53;};
> You will need to stop/edit/start named for this change to take
> effect.This should fix your issues with apt and other applications
> running on the Ubuntu server.
> I agree that you should not be using 123.123.123.0/24 [1]. Please read
> RFC1918 for guidance on private addressing.
>
> tcpdump has a lot of options. For capturing DNS traffic to disk I would
> suggest this as a first pass:
>
> sudo tcpdump -c 1000 -n -i all -w <filename> port 53
>
> This captures all port 53 traffic on any interface (including the
> loopback), stops after 1000 packets (if you don't stop it yourself with
> ctrl-C), writes binary capture data to the file <filename> (you choose
> whatever name you like) and tells tcpdump to *not* attempt to resolve
> addresses to names. This may be irrelevant since it is capturing to
> disk but doesn't hurt.
>
> Over to the Windows machine now. You will not have dig by default. BIND
> for Windows (including utilities like dig) hasn't existed for several
> years. It is still available to download but I *don't* recommend you
> install it.
> Windows nslookup is actually not bad for making test queries,
> especially if used in interactive mode. Again, read the help to see
> what options it has.
> Wireshark can be downloaded and installed for free and I recommend that
> you do that on the Windows machine, so that when you have captured
> traffic on the Ubuntu server, once you have copied the capture file to
> Windows you can open it in Wireshark there. Wireshark can also capture
> packets, like tcpdump, so you can use it to see exactly what your
> Windows machine is doing with DNS.
>
> Hopefully this lot gives you some things to try and also to read, to
> understand the behaviour you are seeing.
> Cheers, Greg
>
> On Sat, 10 May 2025 at 06:01, Danilo Godec via bind-users
> <[email protected]> wrote:
>
> On 10.05.2025 05:29, [email protected] wrote:
>
>> Also check /etc/resolv.conf and see what address(es) is/are listed as
>> nameservers.
>
> The resolv.conf file contains:
>
> nameserver 127.0.0.53
>
> search mydomain.net [2] (where mydomain is my actual domain name and
> not the FQDN of the machine (i.e. "machine01.mydomain.net [3]")).
>
> This was entered by default as BIND was installed. I am wondering if
> the "namesever" should be the machine name on which the server is
> running and not 127.0.0.53 And I gather the 53 on the end has to do
> with the port on which it's listening. I'm not sure if it's correct
> that the 4th octet is substituted like that.
>
> /etc/resolv.conf is not changed or set by BIND, as far as I know it's
> got nothing to do with BIND at all.
>
> IIRC Ubuntu is using 'systemd-resolved' (a local resolver with cache)
> and 127.0.0.53 is the address it listens on, so you might need to check
> that with 'resolvectl dns'.
>
> Then check what is listening on port 53 (netstat -anp | egrep
> ":53.*LISTEN") on the server.
>
> And also check what DNS servers your DHCP sets.
>
> Danilo
>
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Links:
------
[1] http://123.123.123.0/24
[2] http://mydomain.net
[3] http://machine01.mydomain.net
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