Silly question of reverse lookup

[Len Conrad]

 > well. But if I change my default dns to my ISP's dns, I can't reverse
lookup the name in my domain. I think it is normal because I don't think
my ISP's dns will search my dns and find out what ip is corresponding to
what name.

Wolf,

Go to www.SamSpade.org and use the 'ip block' and 'rDNS' tools to lookup 
your DNS's ip.

If rDNS doesn't list the PTR values you have in your db. reverse zone file, 
then your DNS is not being queried because it has not been delegated 
authority for your ip block by the ISP's DNS.  Contact you ISP about 
this.  You cannot fix it by yourself, since you cannot modify your ISP's 
DNS records.

There's a chance that rDNS will return a blank page as many ip blocks don't 
have the reverse records defined at any level of delegation.

Since you are appatenly in Eu, your ISP obtains his ip block from RIPE. 
RIPE has a bot that will visit your DNS as if it was unregistered DNS 
(www.menandmice.com's DNS Expert can do the same) and produce a health 
check before you DNS will be delegated reverse zone authority.  At least, 
that's how European Level3 and I got my /23 delegated.

I suggest that you DL the eval version of DNS Expert and use its 
'unregistered' mode to test you work before calling in the hounds of RIPE.

also use

dig -x ip.ad.re.ss

of you DNS's ip to see whose DNS is authoritative for it.

Len