Re: dns lookup behavior

Monday, 21 February 2022

On Mon, Feb 21, 2022 at 4:52 PM Barry <barry(a)barrys-emacs.org&gt; wrote:

...

 > On 21 Feb 2022, at 20:15, Paolo Galtieri <pgaltieri(a)gmail.com&gt; wrote:
 >
 > Folks,
 >  I have 3 Linux systems, one running F31 and 2 running F34.  On one of
 the F34 systems I have a local DNS server running.  This has worked fine in
 the past, but now I'm seeing strangeness on the 2 F34 systems.
 >
 > I added a host to the DNS server for normal lookup and reverse lookup.
 On the F31 system both:
 >
 > host centos8-opstcore-vm.homenet172-16-96.com
 >
 > and
 >
 > host 172.16.96.20
 >
 > work. The first returns 172.16.96.20 and the second returns
 centos8-opstcore-vm.homenet172-16-96.com.
 >
 > On the F34 which is the DNS server the first works, but the second fails
 with:
 >
 > Host 20.96.16.172.in-addr.arpa. not found: 3(NXDOMAIN)
 >
 > On the other F34 system I get:
 >
 > host 172.16.96.20
 >
 > ;; connection timed out; no servers could be reached
 >
 > The interface has the DNS server pointing to the correct system. If I
 run:
 >
 > nslookup
 > > server 192.168.10.66
 > Default server: 192.168.10.66
 > Address: 192.168.10.66#53
 > > 172.16.96.20
 > 20.96.16.172.in-addr.arpa    name =
 centos8-opstcore-vm.homenet172-16-96.com.
 > >

 Nslookup has been replaced by the dig program.

 Barry

 >
 > Then it works.
 >
 > What do I need to do on F34 systems to get DNS lookups working?

 Might you be using systemd-resolved on the f34 to cache for you?
 What does resolvectl report?

 Barry

 >
 > Any help is appreciated.
 >
 > Paolo
 >

In Fedora 33 DNS resolution was changed (1)adding a DNS server to
/etc/resolv.conf using systemd-resolve.

There is still an /etc/resolv.conf and it is configured to use a name
service running on a loopback device where a local DNS service is listening.

# grep -v '#' /etc/resolv.conf

nameserver 127.0.0.53
options edns0 trust-ad
search domain.com

If you are using the NetworkManager service just add the DNS server address
and it should start working.

Something like this "nmcli con mod $connectionName ipv4.dns "1.1.1.1
9.9.9.9".

At first I didn't like this new way to manage DNS, but I am finding some of
the features to work very well. Like the split dns feature is working
really well with the multiple vpn clients run simultaneously, no more
hacking on /etc/resolv.conf each time a new VPN is started, it just works.

1 - https://fedoraproject.org/wiki/Changes/systemd-resolved

 Regards,
-Jamie