 |  |
> >..does DNS Expert's info indicate
Re: weird dns error resolving "www"
From: andrew kagan
Date: Sunday, September 23, 2001
Time: 10:38:35 am
> >it doesn't hold the zone data, or it's just "nonauthoritative"?
>
> it's answering but without authority.
what does that mean? it's listed as one of the 3 NS records with NetSol a=
nd
it's listed as an NS in the zone record...what makes it "authoritative" o=
r
is this even a problem?
> >Also, if the primary NS _is_ responding, why would it make the resolut=
ion
> >any slower if one of the NS's in non-operational?
>
> If the dead NS is queried first, then the resolver will timeout and the=
n
> try the next. BIND actually queries all NS's and chooses the fastest
one,
> with lowest RTT, round-trip time.
But that's not what was happening...I was seeing an immediate "server cou=
ld
not be found" error when trying to hit the site using "www" through a dia=
lup
connection (but "gas2001.com" resolved immediately")...could that be a
problem with another DNS caching a route to my DNS or something like that=
?
(BTW: I was forced to move a bunch of servers, including the NS box, to a
second location after the WTC disaster...my upstream re-routed my IPs to =
the
new location and I never edited the zone records in any way.)
>
> >Lastly, why is it more desirable to have 2 A records pointing to an IP
> >instead of an A record and a CNAME?
>
> because CNAME's require a second query to retrieve the canonical's A
> record, but more importanlty, CNAME's have rules that many people scre=
w
> up, which breaks their zone (loss of authority).
You saw my zone, and DNS Expert didn't say anything was wrong with using =
the
CNAME record, so why imply that I'm using it inappropriately?
>
> ime, CNAME's seem to be a useless "knob to twist", ie, "oh, I haven=B4t
> twisted any CNAME knobs yet, I better put some in my zone, "just becaus=
e I
> can" " :))
I'm not associating the "www" with a CNAME because I'm trying to show off
how clever I am... I'm doing it because that's what I've told is the corr=
ect
structure for the zone. If you're assuring me now that it's better to hav=
e
multiple A records pointing to the same IP, then I'll do that instead.
>
> btw, your www response pb's might be due not to DNS slow/not responding
but
> the www server or it's last-hop internet link being overwhelmed with ni=
mda
> crap http requests, so that the web server isn't responding at all or
> extremely slowly so that the browsers time out.
I don't think that's the problem...I see a straight-through < 40ms respon=
se
time down to the server when trace routing...and it shouldn't make a
difference that one query is for "gas2001.com" or www.gas2001.com. I'm
certainly no expert on DNS, but it looks more like something along the wa=
y,
either a router or DNS, is either caching a defunct route and not finding=
a
DNS there or the domain record is corrupted somewhere.
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