Problem resolving a domain on my cache server. (part II)

[Mark Andrews]

> Hi Mark,
> 
> Your point looks interesting. I have a question here: When do exactly
> named sends EDNS queries? Once in a while? If yes, in what situations
> EDNS queries are executed?
>  
> I ask this because sometimes my cache server starts not answering
> queries for www.redecard.com.br and that persists for more than 60
> seconds. Last time it happened I had to restart named. After restart it
> starts resolving again.
> 
> Thanks in advance,
> 
> Fabiano

	It sends EDNS queries unless it has a reason not to.
	60-70% of the worlds nameservers process EDNS queries
	today.  Of those that don't most correctly implement
	RFC 1034 and return FORMERR.  Then there are a few that
	return SERVFAIL, NOTIMP or just ignore the OPT record and
	send back a plain DNS answer to a EDNS query.  Then there
	are those servers that just drop EDNS queries.  FORMERR and
	NOTIMP are cachable indications of not understanding EDNS.

	Named falls back to DNS on all the error conditions above.
--
Mark Andrews, ISC
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark_Andrews at isc.org