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

> 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@isc.org