On 2/21/22 14:09, Jamie Fargen wrote:

On Mon, Feb 21, 2022 at 4:52 PM Barry <barry@barrys-emacs.org> wrote:

> On 21 Feb 2022, at 20:15, Paolo Galtieri <pgaltieri@gmail.com> 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Nslookup has been replaced by the dig program.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?

Yes I am

Barry

On the DNS server resolvectl shows:

resolvectl
Global
       Protocols: LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: stub

Link 2 (eno1)
    Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
         Protocols: -DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 192.168.10.66
       DNS Servers: 192.168.10.66 8.8.8.8
        DNS Domain: homenet172-16-96.com homenet172-22-6.com homenet192-10.com

On the other F34 system

resolvecttl
Global
       Protocols: LLMNR=resolve -mDNS -DNSOverTLS DNSSEC=no/unsupported
resolv.conf mode: stub

Link 2 (enp0s20f0u1u1u1)
Current Scopes: LLMNR/IPv4 LLMNR/IPv6
     Protocols: -DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported

Link 3 (enp0s20f0u1u1u4)
    Current Scopes: DNS LLMNR/IPv4 LLMNR/IPv6
         Protocols: +DefaultRoute +LLMNR -mDNS -DNSOverTLS DNSSEC=no/unsupported
Current DNS Server: 192.168.10.66
       DNS Servers: 192.168.10.66
        DNS Domain: homenet172-16-96.com homenet172-22-6.com homenet192-10.com

In all cases it points to the correct DNS server

>
> 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.

The entry for the network device includes the DNS server address

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

I tried this, but reverse lookup still doesn't work.

dig 172.16.96.20

; <<>> DiG 9.16.24-RH <<>> 172.16.96.20
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 47273
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;172.16.96.20. IN A

;; AUTHORITY SECTION:
. 6751 IN SOA a.root-servers.net. nstld.verisign-grs.com. 2022022101 1800 900 604800 86400

;; Query time: 1 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Mon Feb 21 14:39:02 PST 2022
;; MSG SIZE rcvd: 116

dig centos8-opstcore-vm.homenet172-16-96.com

; <<>> DiG 9.16.24-RH <<>> centos8-opstcore-vm.homenet172-16-96.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 26457
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 65494
;; QUESTION SECTION:
;centos8-opstcore-vm.homenet172-16-96.com. IN A

;; ANSWER SECTION:
centos8-opstcore-vm.homenet172-16-96.com. 4778 IN A 172.16.96.20

;; Query time: 0 msec
;; SERVER: 127.0.0.53#53(127.0.0.53)
;; WHEN: Mon Feb 21 14:40:16 PST 2022
;; MSG SIZE rcvd: 85

I tried stopping and restarting systemd-resolved to no avail as well as restarting the network interface also to no avail.

What's curious is for example

host 192.168.10.2 will return a host name most likely because it's cached.

host 172.16.96.20 results in host not found on one F34 system and no servers could be reached on the other F34 system

I ran wireshark on the DNS server and it showed the query to 127.0.0.53 with the hostname and a response of the ip address. But a query to 127.0.0.53 with the ip address returned a not found error.

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
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