need help in bind9 setup

[Chiang Seng Chang]

Hi,

I have a colo machine with 1 ip address and several domain names, I need 
to confirm that I am setting up bind9 correctly. (note. not using actual 
machine name and ip).

name of server: foo.dom-a.com

domains: dom-a.com, dom-b.com

named.conf (the interesting part):

     zone "." {
         type hint;
         file "named.root";
     };

     zone "dom-a.com" in {
         type master;
         file "master/db.dom-a.com";
         allow-query { any; };
     };

     zone "dom-b.com" in {
         type master;
         file "master/db.dom-b.com";
         allow-query { any; };
     };


db.dom-a.com:

     $TTL    86400
     dom-a.com.  IN  SOA     ns hostmaster (...omitted...)
                 IN  NS      ns
                 IN  MX 10   mail
     @           IN  A       1.2.3.4
     localhost   IN  A       127.0.0.1
     ns          IN  CNAME   @
     mail        IN  CNAME   @
     www         IN  CNAME   @
     foo         IN  CNAME   @


db.dom-b.com:

     $TTL    86400
     dom-b.com.  IN  SOA     ns hostmaster (...omitted...)
                 IN  NS      ns
                 IN  MX 10   mail
     @           IN  A       1.2.3.4    ; SAME IP AS dom-a.com
     localhost   IN  A       127.0.0.1
     ns          IN  CNAME   @
     mail        IN  CNAME   @
     www         IN  CNAME   @


notes:

1. dom-a has an extra host foo
2. there is only 1 ip address


Question #2: how do I set up the reverse lookup zone file ?

Obviously the colo is not going to give me a subnet, in fact there is 
only 1 ip.  In this case, do I just setup a

     zone "3.2.1.in-addr.arpa"

and a

     4  IN PTR  foo.dom-a.com.

?

Thank you.

-cs