MCB Systems » dns

Ping Request Could Not Find Host

Mark Berry — Sun, 20 Sep 2009 18:45:45 +0000

Occasionally on my Windows XP Pro SP3 machine, Outlook 2007 SP2 will tell me that it has had an error receiving POP mail from my SBS 2003 server, which resides on the same network.

I started a command prompt and typed “ping myserver.mydomain.local”. Sure enough, I get back the message “Ping request could not find host myserver.mydomain.local. Please check the name and try again.”

An nslookup works fine, so I know the SBS server is there and is responding to DNS requests.

In fact, I can “ping myserver” without problems. But for some reason, pinging the fully-qualified internal name doesn’t work.

Sometimes, I can just type “ipconfig /flushdns” to clear this up. Today that didn’t work. However once I actually stopped and started the DNS cache, ping started working and so did email:

net stop DNScache
net start DNScache

Changing DNS Root Hint for b.root-servers.net

Mark Berry — Thu, 13 Sep 2007 01:44:00 +0000

The Only Thing Constant is Change

On January 29, 2004, the the IP address for the DNS root hint for b.root-servers.net changed to 192.228.79.201:

New IPv4 address for b.root-servers.net

Copy from Server Doesn't Always Copy from Server

I was testing the DNS configuration on two Windows Server 2003 machines. One is R2 SP2; the other is SBS 2003 SP2. In the DNS server's properties, on the Root Hints tab, I clicked on the Copy from Server button and copied from 4.2.2.2 (a Level 3 DNS server). However, this did not update the address for b.root-servers.net; it still showed the old 128.9.0.107. So when I ran dcdiag /test:dns, it reported an error on accessing b.root-servers.net.

I tried removing b.root-servers.net and copying from 4.2.2.2. This time, b.root-servers.net showed up with IP Address “Unknown”. This is strange, since I can use nslookup against 4.2.2.2 and get the correct address for b.root-servers.net. Apparently 4.2.2.2 does not let you copy root hints, although no error is displayed.

Next I tried copying from my ISP's DNS server. This worked, but it did not replace the old IP address; it just added the new one.

The bottom line is that once you get your root hints set up, you'd better double-check them against the official list here.

Old DCDiag Raises False Alarms

Another “gotcha” I encountered is that the original DCDiag program in Windows Server 2003 Support Tools was telling me that all of my root hints were bad. Microsoft Support suggested updating to the SP2 version of Support Tools, which did in fact fix that problem.

DNS Root Hints and Forwarders

Mark Berry — Thu, 05 Jul 2007 05:04:00 +0000

A post in the Yahoo group mssmallbiz asked an interesting question: when DNS Forwarders are configured under SBS 2003, is there a way to get the secondary nameserver to automatically take over when the primary is unavailable?

Don't Use Forwarders

The answer was simple: don't use forwarders. Go to Start > Administrative Tools > DNS, go into the Properties for the server, go to the Forwarders tab, and click Remove until they are gone.

Do Use Root Hints

Then make sure the root hints are up to date. The poster suggested using Windows Update. I didn't see root hints there, but I found a simple way to refresh them: in the DNS Properties, go to the Root Hints tab, click on Copy from Server, and enter 4.2.2.2 as the IP address to copy the hints from.

Posters seemed to think that relying solely on root hints is actually faster for resolving external DNS queries.

The instructions work for Windows Server 2003 as well as SBS 2003!

Update: copying root hints from 4.2.2.2 doens't work. See this post for details and a solution.