> > > > I run a small web and email hosting service. My ISP provides me
> > > > with a very small block of static IP's. I run my own DNS servers.
> > > > HOWEVER, I cannot get my ISP to properly delegate reverse DNS
> > > > lookups. (Huge sigh). A reverse DNS on my IP gets a single valid
> > > > response, which is some made-up name provided by the ISP. With me
> > > > so far?
> a very small is probabli less tha 254 addresses.
Yes, 8. With Virtual Hosting and NAT, I don't need any more.
> Since reverse lookup is done in batches of 256 addresses the
> reverse delegation if for a group of customers.
> So unless you cannot get a full calss C subnet, you cannot get
> your reverse.
Reverse lookup need not be done in batches of 256. There are
well-known (well, at least published) methods of setting up
reverses for smaller blocks. See Bind 9 users group; Cricket Liu's
DNS & Bind textbook, etc. But try explaining this to a big
company that doesn't really care... (No kidding, I emailed them
chapter and page number, and ISBN number of the textbook!)
> The reverse lookup should be made then in this way: get the
> declared address, than make a reverse lookup. if this lead to
> another hostname do a direct lookup on this other name , if at least
> for this reverse and forward correpond, it is all ok.
>
> Leonardo Boselli
> nucleo informatico e telematico
> Dipartimento Ingegneria Civile
> Universita` di Firenze
> V. S. Marta 3 - I-50139 Firenze
> tel +39()0554796431
> cel +39 3488605348
> fax +39()055495333
> http://www.dicea.unifi.it/~leo
I think that would be quite reasonable.
How about simply doing a forward lookup on the hostname
declared at EHLO, and verifying that the IP address of the
associated DNS A record (a) exists, and (b) is the same as
the machine actually trying to connect? Would that not be
adequate? I have not yet been made to understand when
a reverse lookup would buy anything, especially since so
many large ISPs don't set up reverse DNS entries correctly.
Jim Roberts
Punster Productions, Inc.
