Authoritative server recursing?

Hello,

I'm seeing this strange problem, maybe it's me... but it's the first time I
see such behaviour.

I have an authoritative master name server for the 10.212.62.in-addr.arpa
The zone contains a 16.10.212.62.in-addr.arpa IN NS record with
mix.b-soft.it

Another autoritative slave server has older, incorrect data.

The master server can recurse though it's not used as a resolver.

Here is the strangeness:

stef:~ # dig @vega -x 62.212.10.16 NS

; <<>> DiG 9.2.2 <<>> @vega -x 62.212.10.16 NS
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 33042
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;16.10.212.62.in-addr.arpa. IN NS

;; ANSWER SECTION:
16.10.212.62.in-addr.arpa. 85140 IN NS
mix.b-soft.com.16.10.212.62.in-addr.arpa.
16.10.212.62.in-addr.arpa. 85140 IN NS
zagor.b-soft.com.16.10.212.62.in-addr.arpa.

;; Query time: 2 msec
;; SERVER: 62.212.0.2#53(vega)
;; WHEN: Wed Jun 1 16:17:14 2005
;; MSG SIZE rcvd: 92

------------------------------------------------------

stef:~ # dig +norecurse @vega -x 62.212.10.16 NS

; <<>> DiG 9.2.2 <<>> +norecurse @vega -x 62.212.10.16 NS
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 35930
;; flags: qr ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; QUESTION SECTION:
;16.10.212.62.in-addr.arpa. IN NS

;; AUTHORITY SECTION:
16.10.212.62.in-addr.arpa. 86400 IN NS mix.b-soft.com.

;; ADDITIONAL SECTION:
mix.b-soft.com. 171528 IN A 62.212.3.230

;; Query time: 1 msec
;; SERVER: 62.212.0.2#53(vega)
;; WHEN: Wed Jun 1 16:17:26 2005
;; MSG SIZE rcvd: 87

In other words, if I ask for recursion, the master server asks to the slave
and returns data from it. If I don't ask for recursion it responds
correctly.

The same happens if I disable recursion on the master.

Any idea?

thanks!

--
Daniele Orlandi