CNAME and other data

Phil Benchoff

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Jun 5, 1996, 3:00:00 AM6/5/96

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I get a number of "xxx has CNAME and other data (illegal)" messages
when loading the database. I understand why an A or MX RR would
be illegal, but the records in question are TXT. Is this really
a problem?

Phil

Mathias Koerber

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Jun 7, 1996, 3:00:00 AM6/7/96

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On 5 Jun 1996, Phil Benchoff wrote:

yes, a CNAME hides *all* data under the same label, and forces the
resolver to look up *everything* under the new label:

If you have:

thislabel IN CNAME thatlabel

thislabel ---CNAME------------>thatlabel A 2.3.4.5
hides the below: thatlabel TXT "thisisit"
thislabel A 1.2.3.4
thislabel TXT "unused"

Thus a lookup under (thislabel,TXT) will return "thisisit", and the
(thislabel,A) will return 2.3.4.5...

| Phil
|

Mathias Koerber | Tel: +65 / 471 9820 | mat...@singnet.com.sg
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Christopher Davis

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Jun 7, 1996, 3:00:00 AM6/7/96

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PB> == Phil Benchoff <benc...@ngw.cns.vt.edu>

PB> I get a number of "xxx has CNAME and other data (illegal)" messages
PB> when loading the database. I understand why an A or MX RR would be
PB> illegal, but the records in question are TXT. Is this really a
PB> problem?

Yes.

A CNAME record is a pointer to another place in the DNS. It points ALL
records asked for at its name to the "real" or canonical name.

If someone does a TXT query for that name, should it return the TXT record
you list, or the TXT record at the target of the CNAME (if any)? That
situation is ambiguous, and therefore prohibited.

Don Lewis

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Jun 7, 1996, 3:00:00 AM6/7/96

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On Jun 5, 2:09pm, Phil Benchoff wrote:
} Subject: CNAME and other data

} I get a number of "xxx has CNAME and other data (illegal)" messages

} when loading the database. I understand why an A or MX RR would

} be illegal, but the records in question are TXT. Is this really
} a problem?

Yes. Assume that I am a caching client. I send your server a CNAME
query for xxx.some.domain, and get the response:
xxx.some.domain IN CNAME yyy.some.domain
If at some later time, I decide to do a TXT query for xxx.some.domain,
I'll find the CNAME RR in my cache and just send your server a TXT query
for yyy.some.domain. I'll have no way of knowing that you have a TXT RR
belonging to xxx.some.domain.

--- Truck

Mark Andrews

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Jun 8, 1996, 3:00:00 AM6/8/96

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> I get a number of "xxx has CNAME and other data (illegal)" messages
> when loading the database. I understand why an A or MX RR would
> be illegal, but the records in question are TXT. Is this really
> a problem?
>

> Phil
>
It applies to ALL types.

Mark
--
Mark Andrews, CSIRO Div Maths & Stats
Locked Bag 17, North Ryde, NSW 2113, Australia.
PHONE: +61 2 325 3148 INTERNET: ma...@syd.dms.csiro.au
MOBIL: +61 41 942 9884 UUCP:....!uunet!syd.dms.csiro.au!marka

Dave Barr

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Jun 10, 1996, 3:00:00 AM6/10/96

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In article <4p44ek$1...@solaris.cc.vt.edu>,

Phil Benchoff <benc...@bev.net> wrote:
>I get a number of "xxx has CNAME and other data (illegal)" messages
>when loading the database. I understand why an A or MX RR would
>be illegal, but the records in question are TXT. Is this really
>a problem?

No, but named is telling you that it's throwing away the "other data"
(in your case TXT records). Remove the TXT records associated
with aliases and named won't generate the error anymore.

--Dave