Re: paging all socket geniuses
- From: Tim Bradshaw <tfb+google@xxxxxxxx>
- Date: Thu, 31 Jul 2008 08:20:34 -0700 (PDT)
On Jul 30, 2:31 am, Kenny <kentil...@xxxxxxxxx> wrote:
[long pauses, hostnames, numbers]
This will be name lookup timesouts. Almost certainly it is reverse
name lookup timeouts: something is trying to resolve an IP address
into a name, and you're getting a timeout (almost certainly a DNS
timeout) while doing this.
I don't have access to a Windows box (mac person at home, solaris at
work now), but I think they have nslookup.
So, if you get a command prompt on the machine, then you want to test
two things. For a fully qualified name x (s3.amazonaws.com say) do a
forward lookup:
nslookup -q=any x.
Note that full-stop: I mean that.
That should work and come back with some stuff. It may be a CNAME not
an IP address, if it is chase the CNAME down by making the same query
on it. For the above address you end up with a bunch of IP addresses,
one of which is 72.21.203.129.
Now pick that IP address, turn it round and do a pointer lookup:
nslookup -q=ptr 129.203.21.72.in-addr.arpa.
And you should get back a name.
Now try the equivalent reverse lookup for the IP address of the box
itself.
Chances are that one of these will go away for really a long time, and
then come back with some failure indication. If that happens, then
the problem is that DNS is screwed somewhere.
Fixing it is unfortunately out of the scope of this article (it is
probably either the ISP or whatever is telling the machine its DNS
servers, which will generally be the a DHCP server), but you should at
least now have a feel for what the problem is.
--tim
.
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