in-addr.arpa reverse lookup db files w/ Class B subnet

[Phil Olson]

Hello,
I am trying to setup an Intranet on my LAN with a single zone
(intranet.org.), and am trying to determine what my db files should look
like.  I have 2 subnets, 172.16.0.0/16, and 172.17.1.0/24.  What I am not
sure about is how the reverse mapping files (in-addr.arpa.) should look
like.  Here is my first attempt at the following files: db.intranet,
db.172.16, and db.172.17.1.  What I am not sure on is: since my first subnet
is a full class B, should the file be named db.172.16, or db.172.16.0?  And
inside of that file, should the PTR record for 172.16.0.10 read
10 IN PTR mail.intranet.org.

OR

0.10 IN PTR mail.intranet.org.  ?

I looked in the dns and bind book from O'Reilly but it only had examples of
subnets with a /24 mask.  Thanks in advance.

-Phil


; file db.intranet
@ IN SOA ns1.intranet.org. hostmaster.mail.intranet.org. (
   1 ; Serial
   10800 ; Refresh after 3 hours
   3600 ; Retry after 1 hour
   604800 ; Expire after 1 week
   86400 ) ; Minimum TTL of 1 day

; Name Servers
 IN NS ns1.intranet.org.
 IN NS ns2.intranet.org.

; Addresses for the canonical names
localhost IN A  127.0.0.1
mail  IN A  172.16.0.10
home  IN A  172.16.0.16
ns1  IN A  172.16.0.17
ns2  IN A  172.16.0.18
smtp  IN A  172.17.1.4
web  IN A  172.17.1.5

; MX Records
intranet.org. IN MX 10 mail.intranet.org.

; file db.172.16
@ IN SOA ns1.intranet.org. hostmaster.mail.intranet.org. (
  1 ; Serial
  10800 ; Refresh after 3 hours
  3600 ; Retry after 1 hour
  604800 ; Expire after 1 week
  86400 ) ; Minimum TTL of 1 day

; Name Servers
 IN NS ns1.intranet.org.
 IN NS ns2.intranet.org.

; Addresses point to canonical name
10 IN PTR mail.intranet.org.
16 IN PTR home.intranet.org.
17 IN PTR ns1.intranet.org.
18 IN PTR ns2.intranet.org.


; file db.172.17.1
@ IN SOA ns1.intranet.org. hostmaster.mail.intranet.org. (
  1 ; Serial
  10800 ; Refresh after 3 hours
  3600 ; Retry after 1 hour
  604800 ; Expire after 1 week
  86400 ) ; Minimum TTL of 1 day

; Name Servers
 IN NS ns1.intranet.org.
 IN NS ns2.intranet.org.

; Addresses point to canonical name
4 IN PTR smtp.intranet.org.
5 IN PTR web.intranet.org.