CNAMEs and ip-addr.arp

[Barry Margolin]

In article <c0tld8$iaf$1 at sf1.isc.org>, tnaves at linkwest.net wrote:

> I have a host with an A record:
> 
> host IN A 192.168.1.50
> 
> I have two others which are aliases of host:
> 
> hostess	IN CNAME host
> mostess	IN CNAME host
> 
> in db.1.168.192.in-addr.arpa I have a PTR reord for host:
> 
> 50.1.168.192 IN PTR host
> 
> My question is:
> 
> Is there a way to have reverse lookup records for hostess and mostess,
> which are aliases of host?

No, PTR records are required to point to primary names, not aliases.

You could change the aliases to A records:

hostess IN A 192.168.1.50
mostess IN A 192.168.1.50

and then add corresponding PTR records:

50.1.168.192 IN PTR host
             IN PTR hostess
             IN PTR mostess

But why do you think you need to do this?  It doesn't scale very well, 
and it's generally not necessary.  It makes reverse lookups 
unpredictable, because most applications just use the first name they 
get back, and round-robin means that this could be any one of those 
names.

-- 
Barry Margolin, barmar at alum.mit.edu
Arlington, MA