Host unknown errors occuring sporadically

Host unknown errors occuring sporadically

Post by Chris Moor » Thu, 27 Mar 2003 09:06:26



Hi,
My organization is running Windows 2000 with Exchange 5.5 sp4.  I recently
migrated our internal DNS servers from the primary/secondary configuration
to active directory integrated (before and after the DNS servers were set to
forward requests to the ISPs DNS server).  At the same time I uninstalled
the DNS server service from my mail server.  However, when I did this my
mail server started generating an unusual number of host unknowns for email
external to the company.
It appeared that the initial problem was that when I converted from the
standard DNS configuration to active directory it wasn't "responding" to the
mail server, which is not a DNS server (by responding I mean that when I
tried to use the nslookup utility from the mail server it got a query
refused).  I did two things to correct this issue (based on the information
that I got from the newsgroup and the knowledgebase), which was to configure
DNS so that the mail server would be capable of making zone transfer
requests so that the nslookup utility would work.  The second was to change
the ip configuration of the mail server so that the first two DNS servers
are my IP's DNS servers (our internal DNS server is listed third).  However,
while this lowered the number of failures on the host name (both through
NDRs indicating host unknown and the nslookup utility not finding the domain
or timing out) we still continue to get a higher number than before.  The
weird thing is that I will do an nslookup a couple times in a row and get a
time out one time and then a resolution the next.  I've also used external,
web-based nslookup tools and they find the domains consistently.
Considering the timing of the problem I'm assuming that it is probably
something to do with the configuration change to the DNS server, but I'm not
really sure where to go forward on troubleshooting the problem.  I am a
little suspicious that part of the problem might lie with my ISP's DNS
server (I will set the nslookup utility to query them directly and they are
inconsistent).  If anyone has any other suggestions I would appreciate it.
Thanks in advance.
-Chris Moore
P.S. We will be switching ISPs at the end of the month so "maybe" that will
alleviate the problem.
 
 
 

1. Host Unknown or Error during Host Resolution

Hello,

I am using Exchange Server 5.5 behind Proxy Server 2.0.

During busy periods I get a large number or "Host Unknown" or "Error during
Host Resolution".  It's like it can't talk with the DNS server.  Any ideas
how to prevent this from happening.  I have three enties in this order 1) A
DNS server used by my ISP, 2) A DNS server used by another ISP, 3)My
internal network DNS server.  I'm permenantly connected via a 128K
fractional T-1 so I do have limited bandwidth.

The messages eventually go through, but impatient users are resending the
messages and creating lots of bottlenecking.

Thanks for any help,
John Hawkins

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