[lug] Re: Virtual Hosting

[Nate Duehr]

The alternative is not to have any reverse records (PTR) at all.

Nate

Quoting John Hernandez <John.Hernandez at noaa.gov>:

> Given our hypothetical scenario (where there is not a 1-to-1 mapping of
> name-to-address, rather a many-to-1 mapping), you're basically forced to
> pick one of those names for reverse lookup purposes, aren't you?  What
> would be the alternative?
> 
> A typical client app provides an IP address to the server upon
> connection (in the form of an IP source address).  The order of lookups
> (for a paranoid server) is then address -> name, and then resulting-name
> -> address, not the other way around as you suggested.  Servers are
> generally happy when address(in) == address(out), as you correctly
> stated, but that condition is satisfied by setting your PTR RR value to
> any one of the set of valid A RR keys.
> 
> rm at mamma.varadinet.de wrote:
> > 
> > On Wed, Mar 14, 2001 at 12:18:05PM -0700, John Hernandez wrote:
> > > For the purpose of reverse DNS lookup, you can generally pick any of
> the valid A RR keys for a particular IP address.  As long as a reverse
> -> forward lookup yields a result (IP address) equivalent to your
> initial input, services configured to be paranoid should be satisfied.
> > 
> > I would actually advise _against_ picking any A records for setting
> > up reverse lookups. Some services get really upset if the reverse
> > lookup yields strange results (esp. if they do double lookup for
> > security reasons name->address and then address->name. If the address
> > that comes out at the end doens't match the initial one you might
> > have a problem). Most of the java VMs embedded in browsers will
> > only allow an applet to request an URL if the host part of the
> > URL is the same as the hopst part of the applets URL. It's easy
> > to imagine what happens when a cautious security manager starts
> > interacting with strange reverse lookups.
> > 
> >  Ralf
> > 
> > >
> > > -John
> > >
> > > Justin wrote:
> > > >
> > > > In BIND 8.2.x the only file that relates to what you're talking
> about
> > > > is your reverse zone file. It's the file that maps the ip's back
> to
> > > > specific A record host names. As far as virtual hosting I don't
> believe
> > > > you can have a file like this for virtual use. After all, virtual
> hosts
> > > > don't really have their own ip address, they map back to another
> > > > machines A record ip address. Which, in turn, that ip address must
> > > > reverse lookup to it's respective host as defined by that A
> record. I
> > > > think this stuff is in a BIND RFC somewhere, but I'm sure. I also
> may
> > > > be way off here, but this has been my understanding since I can
> > > > remember...
> > > >
> > > > Justin
> > > >
> > > > > It was my understanding that all the virtual hosts are listed in
> one
> > > > > file and that file is pointed back to the server IP.  Maybe it
> > > > > involves the $INCLUDE directive?
> > > > >
> > > > > Note: When you reply to this message, please include the mailing
> > > > >       list/newsgroup address in Cc: and my email address in To:.
> > > > >
> > > > >
> *********************************************************************
> > > > > Signed,
> > > > > SoloCDM
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> > > > >
> > > >
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--
Nate Duehr, nate at natetech.com

"Never underestimate the bandwidth of a 747 filled with CD-ROM's."