Strange dns lookup problem, please help.

  • Thread starter Thread starter davidw
  • Start date Start date
D

davidw

I found sometime my server can not ping at least one domain, while I can
always ping it from my home machine.

so I ping www.thedomain.ca, it returns unknown host, I then ping the dns
server of the domain, like ping dns1.anotherdomain.org, it returns unknown
host too. I found I can ping their IP without problem, so the problem is it
can not get IP from the domain names. I have local dns for my server. If I
go to the dns server and clear it Cached Lookups, I can ping those domains
well, so looks like the problem is the Cached lookups.

Under the cached lookups, I can see entries like

ca
thedomain
(same as parent folder) NS dns1.anotherdomain.org.

and

org
anotherdomain
(same as parent folder) NS ns1.nbc.netcom.ca.

Any idea what maybe wrong? once I clear the cached loopups, it works, but
after a while (not sure how long), it will stop working again.

Thanks!
 
Hi,

and how does your "forwarders" and "root hints" configuration looks like ?
Do you use any of them ?

Right click your DNS server in the DNS console and check what you have on
"Forwarders" and "Root hints" tab. Are there any entries which point to the
"upper" DNS servers ( eg. ISP's Dns servers ) ?

Regards
Dominik Zurek
 
Thanks.

I have two internal dns servers and two dns servers for outside. The
internal dns servers has forwarder set to external server. And there are a
list of ip under Root Hint. But I remember no long ago, I turned on
"disabled recursion" on both external servers. I am not sure if that is the
cause. I did that according result from dnsstuff.com
 
davidw said:
Thanks.

I have two internal dns servers and two dns servers for outside. The
internal dns servers has forwarder set to external server. And there
are a list of ip under Root Hint. But I remember no long ago, I
turned on "disabled recursion" on both external servers. I am not
sure if that is the cause. I did that according result from
dnsstuff.com
Click to expand...

If you disabled recursion on the external DNS servers, you can no longer use
them as a forwarder(except as a conditional forwarder).
If the external DNS servers are behind the same NAT device, you will need to
create the same zones on the internal DNS servers, or configure Conditional
Forwarding on the internal DNS for the zones the external DNS hold.
 
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