Litmus Test: Can You Troubleshoot DNS?
Professionals Take the Time to Master Their DNS Settings
Amateurs use WINS where ever possible and avoid DNS
Way back in the days of NT 3.5, DNS was an afterthought and relegated to the option pack. By the time of NT 4.0, DNS, was a useful if peripheral service installed from the Windows Components. Nowadays with Windows Server 2003, you cannot even install Active Directory without being an expert in DNS. During these ten years, WINS has steadily declined, until now it only has a very minor role for Windows 98 clients and some Exchange servers.
At its simplest, DNS is responsible for mapping IP addresses to machine names. Forexample in, the DNS database there could be a host record (Type = A) for a machine called London with an IP address of 192.168.0.230.
To truly master DNS you must invest time in the learning the terminology and practice configuring, Reverse Lookup, Zone, Active Directory Integration and other specialist DNS settings.
In Windows Server 2003, DNS can dynamically update its own host records – hence the acronym DDNS. Thisovercomes a limitation of DNS in NT 4.0 and allows WINS to be phased out in pureWindows Server 2003 networks. The only real use of WINS is for organizations with distributed Exchange servers.
DNS and Active Directory
DNS holds SRV or Service records which enables desktop computers and servers to find domain controllers that are providing specific services. For example, Global Catalog and Kerberos are need for logon authentication; DNS returns the IP address of domain controller offering those services.
By integrating AD and DNS you reduce network traffic because only new orchanged records are updated. This is known as incremental zone transfer (IXFR). In NT 4.0, the whole database was send over the network even if just one recordchanged.
How to change to AD zones? right-click the DNS Zone, Properties,General Tab.
For troubleshooting DNS
- Check out the new Monitoring tab; right-click the DNS SERVER, Properties.
- If DNS is not working, revert to the Host file (Winnt\system32\drivers\etc\hosts
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Secure Your DNS Server – Litmus Test
Amateurs allow people to pollute their DNS server with rogue zone transfers.
Professionals secure their DNS server from unauthorized zone transfers.
To see if DNS is configured securely, try this:
- Open a command prompt
- Type nslookup
- Set type=all
- Enter domain such as Microsoft.com
You will see the nameservers
- Type server ns1.microsoft.com
- Then type ls -d Microsoft.com
You will get an error because it won’t let you do a zone transfer to your machine, but you would be amazed how many domains still do!
Kindly sent in by Harold Stultiens. See more readers tips.
Litmus Test: Professionals Phase Out WINS
WINS is a Microsoft method for resolving names to IP addresses. As you have probably guessed I do not like WINS!
WINS is no longer needed in a pure Windows Server 2003 and XP networks. This is because DNS can handle the name resolution and find all the resources XP and W2K Pro need. However WINS still has a role in enabling Windows 9x clients to find their logon servers. To be fair, WINS has always allowed dynamic updates, but with DDNS clients can automatically change their IP registrations in DNS.
WINS will be phased out in Exchange 2007 and Longhorn.
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Over 40 of Guy’s litmus tests. Have fun while you learn about aspects of computing. Stacks of ideas to check your servers, networks and security.
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Guy’s Litmus test is a concept that you can apply anywhere. Each test gives you an instant answer to the simple question:- ‘Are you dealing with a professional, or are they an amateur? Is this the real deal, or is it a turkey?’ The Litmus Test concept is rather like Best Practice, but it reduces a 27 page report to one sentence.