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I'm having trouble querying a name server on a different network 192.168.56.0/24 for records that contain host, vm1, vm2, and vm3. And I do not understand why. Is there anyway someone can explain whats going on.

Ferrari

/etc/resolv.conf

# Generated by NetworkManager
search luxury.auto.ops
nameserver 172.45.20.3
nameserver 192.168.56.2

/etc/hosts

127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4
::1 localhost localhost.localdomain localhost6 localhost6.localdomain6
172.45.20.1 host
172.45.20.1 host host.oadese.ops

/etc/named.conf

options 
 directory "/var/named";
 allow-query 127.0.0.1; 172.45.20.0/24; 192.168.56.2;;
 forwarders 192.168.56.1; ;
;

zone "localhost"
 type master;
 file "named.localhost";
;

zone "luxury.auto.ops."
 type master;
 file "mydb-for-luxury-auto-ops";
 allow-transfer 172.45.20.4; ;
;

zone "20.45.172.in-addr.arpa." 
 type master;
 file "mydb-for-172.45.20";
;

vi /etc/sysconfig/network-scripts/ifcfg-eth0

TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=static
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
NAME=eth0
UUID=78aa1a9b-0607-492a-b7dc-55d6f76f05d5
DEVICE=eth0
ONBOOT=yes
DOMAIN=luxury.auto.ops
IPADDR=172.45.20.3
NETMASK=255.255.255.0
HWADDR=52:54:00:8d:9e:93
GATEWAY=172.45.20.1
DNS1=172.45.20.3
DNS2=192.168.56.2

vm1 192.168.56.2

/etc/named.conf

options 
 directory "/var/named";
 allow-query 127.0.0.1; 192.168.56.0/24; 172.45.20.0/24;;
 forwarders 192.168.56.1; ;
;

zone "localhost"
 type master;
 file "named.localhost";
;

zone "oadese.ops" 
 type master;
 file "mydb-for-oadese-ops";
;

zone "56.168.192.in-addr.arpa." 
 type master;
 file "mydb-for-192.168.56";
;

/var/named/mydb-for-oadese-ops

$TTL 3D
@ IN SOA vm1.oadese.ops. hostmaster.oadese.ops.(
 2016010301 ; Serial
 8H ; Refresh
 2H ; Retry
 1W ; Expire
 1D ; Negative Cache TTL
);
@ IN NS vm1.oadese.ops.
vm1 IN A 192.168.56.2
vm2 IN A 192.168.56.3
vm3 IN A 192.168.56.4
host IN A 192.168.56.1

[root@ferrari ~]# nslookup vm1
Server: 192.168.56.2
Address: 192.168.56.2#53

Non-authoritative answer:
Name: vm1
Address: 192.168.56.2

[root@ferrari ~]# nslookup vm2
Server: 192.168.56.2
Address: 192.168.56.2#53

Non-authoritative answer:
Name: vm2
Address: 192.168.56.3

[root@ferrari ~]# nslookup vm3
Server: 192.168.56.2
Address: 192.168.56.2#53

Non-authoritative answer:
Name: vm3
Address: 192.168.56.4

[root@ferrari ~]# nslookup host
Server: 192.168.56.2
Address: 192.168.56.2#53

Non-authoritative answer:
Name: host
Address: 192.168.56.1

[root@ferrari ~]# nslookup ferrari
Server: 172.45.20.3
Address: 172.45.20.3#53

Name: ferrari.luxury.auto.ops
Address: 172.45.20.3

[root@ferrari ~]# host vm1
Host vm1 not found: 3(NXDOMAIN)
[root@ferrari ~]# host vm2
Host vm2 not found: 3(NXDOMAIN)
[root@ferrari ~]# host vm3
Host vm3 not found: 3(NXDOMAIN)
[root@ferrari ~]# host host
[root@ferrari ~]# host ferrari
ferrari.luxury.auto.ops has address 172.45.20.3

Mar 18 10:43:50 ferrari named[2242]: error (connection refused) resolving 'vm1.oadese.ops/A/IN': 192.168.56.2#53
Mar 18 10:43:50 ferrari named[2242]: error (network unreachable) resolving 'vm1.oadese.ops/A/IN': 2001:500:2f::f#53
Mar 18 10:43:50 ferrari named[2242]: error (connection refused) resolving './NS/IN': 192.168.56.2#53
Mar 18 10:43:50 ferrari named[2242]: error (network unreachable) resolving './NS/IN': 2001:500:2f::f#53
Mar 18 10:43:51 ferrari named[2242]: error (connection refused) resolving 'vm1/A/IN': 192.168.56.2#53
Mar 18 10:43:51 ferrari named[2242]: error (network unreachable) resolving 'vm1/A/IN': 2001:500:1::803f:235#53
Mar 18 10:43:51 ferrari named[2242]: error (network unreachable) resolving 'vm1/A/IN': 2001:7fe::53#53

In the second nameserver you defined a forwarder for the server itself. For your architecture should be:

forwarders 172.45.20.3 ;

There is also the matter of the search directive in /etc/resolv.conf; if you have got two domains, and only one there. For the resolver to try and add the domains to the queries for both of the domains, you have to use:

search luxury.auto.ops. oadese.ops.

By the way, do not forget the dots.

Furthermore, you are configuring VMs to ask different nameservers with different views. DNS resolvers do not work like that, the 2nd nameserver will only be used if the 1st one is down. If the 1st is up and says it does not know a DNS address, the 2nd one won't be queried.

If you want to have separated DNS domains in separated nameservers, make the domain of the other server a slave, and make it a master on the other server; other more cleaner choice is making one of the servers a master for the two domains, and the other a slave.