CentOS - Feb 2018 - Unbound question: forward-zone and stub-zone

Hi all,

 I have a strange case with unbound ... I have defined a stub-zone to query to a
secondary DNS server:

stub-zone:
	name: "mydomain.org"
	stub-addr: 172.22.54.4

stub-zone:
	name: "54.22.172.in-addr.arpa."
	stub-addr: 172.22.54.4

 ... but it doesn't works: any hostname or IP address is resolved. But if I
use "forward":

forward-zone:
	name: "mydomain.org"
	forward-addr: 172.22.54.4

forward-zone:
	name: "54.22.172.in-addr.arpa."
	forward-addr: 172.22.54.4

 all works ok. Then, which is the real difference between stub and forward
zones?

 According to unbound's man page, stub-zone is used for authority servers,
which is my case. But forward zones are valid for not authority servers. On the
other side: "unbound performs the recursive processing itself for stub
zones." ?????? How?? Why?? If I use a stub-zone, it is because I have an
authority server with recursion for its SOA domain ...

 I don't understand ... What is the correct configuration?

-- 
Greetings,
C. L. Martinez