CNAME problems

[Mark_Andrews at isc.org]

> In article <7li5a3.1g56.2 at verdi.nethelp.no>, sthaug at nethelp.no (Steinar
> Haug) wrote:
> 
> >[Murray Walker]
> >
> >|   The only definite solution is to follow the qmail rule which states that
> >|   dns ANY queries should return less than 512 bytes. I took out some TXT
> >|   records from our dns that were getting returned with the query. I think
> >|   that may have solved the problem - although I'm not entirely convinced
> >|   yet. 
> >
> >Unfortunately, the serial number wasn't updated, as far as I can see. Thus
> >liddell.cstr.ed.ac.uk returns an answer of 489 bytes (which is below the
> >512 byte limit) with serial # 1999179327, while xlab-0.ed.ac.uk returns an
> >answer of 895 bytes (also serial # 1999179327).
> 
> As the hostmaster of xlab-0.ed.ac.uk I'm not sure how it can be returning
> (as it apparently is) a UDP answer >512 bytes.  It's running the same
> software (BIND 4.9.7 - due an upgrade shortly) as other servers which are
> secondaries for cstr.ed.ac.uk.  Any ideas?  It's due to get an ndc restart
> shortly so if the answers aren't quick the evidence may be gone.
> 

	It is *not* reporting an answer bigger that 512 bytes via UDP.
	All BIND based resolver libraries have supported TCP retry since
	at least the BIND 4.8 days.  You have to take special steps to
	stop it retrying via TCP.  Note the +ignore (ignore truncation
	errors) on the dig command below.

	BIND 8 introduced TCP retries into the server code.

	As for the different answers you have been told at least three
	times to increment the serial number for the zone.

	Mark
	
; <<>> DiG 8.2 <<>> any cstr.ed.ac.uk @xlab-0.ed.ac.uk +norec +ignore 
; (2 servers found)
;; res options: init igntc defnam dnsrch
;; got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 48445
;; flags: qr tc ra; QUERY: 1, ANSWER: 11, AUTHORITY: 0, ADDITIONAL: 0
;; QUERY SECTION:
;;	cstr.ed.ac.uk, type = ANY, class = IN

;; ANSWER SECTION:
cstr.ed.ac.uk.		15M IN SOA	liddell.cstr.ed.ac.uk. postmaster.cstr.ed.ac.uk. (
					1999179327	; serial
					2H		; refresh
					10M		; retry
					1w1d		; expiry
					15M )		; minimum

cstr.ed.ac.uk.		15M IN NS	liddell.cstr.ed.ac.uk.
cstr.ed.ac.uk.		15M IN NS	cancer.ucs.ed.ac.uk.
cstr.ed.ac.uk.		15M IN NS	xlab-0.ed.ac.uk.
cstr.ed.ac.uk.		15M IN NS	dns.dcs.ed.ac.uk.
cstr.ed.ac.uk.		15M IN NS	pcserver2.ed.ac.uk.
cstr.ed.ac.uk.		15M IN NS	dns2.dcs.ed.ac.uk.
cstr.ed.ac.uk.		15M IN TXT	"Zone generated by root (maw) on Tue Jun 29 10:55:16 1999"
cstr.ed.ac.uk.		15M IN TXT	"University of Edinburgh Centre for Speech Technology Research"
cstr.ed.ac.uk.		15M IN TXT	"General queries to support at cstr.ed.ac.uk"
cstr.ed.ac.uk.		15M IN TXT	"Mail queries to postmaster at cstr.ed.ac.uk"

;; Total query time: 614 msec
;; FROM: bsdi.dv.isc.org to SERVER: xlab-0.ed.ac.uk  129.215.168.33
;; WHEN: Wed Jul  7 09:14:15 1999
;; MSG SIZE  sent: 31  rcvd: 468

> -- 
> Sam Wilson
> Network Services Division, Computing Services
> The University of Edinburgh
> Edinburgh, Scotland, UK
> 
> 
--
Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: marka at isc.org