DNSNotes

DNSNotes

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General

If the person responsible for administering a DNS zone should change, make sure you modify the SOA record for the zone to update the email address of the zone administrator. The DNS Server service sends email to this address automatically when query errors and other conditions arise. Note that the email address substitutes the usual at symbol (@) with a period (.); e.g., specify info .mtit.com instead of [e-mail] .

DNS replaces the Hosts file, which was the original method for performing hostname-to-IP address name resolution on a TCP/IP network. However, the Hosts file can still be used in smaller WS2003 networks instead of DNS if desired, such as in a small intranet with no connection to the Internet.

You can start, stop, pause, and resume name servers by:

Right-click DNS server All Tasks {Start Stop Pause Resume Restart}

net stop dns net start dns net pause dns net continue dns

Zones

Always have at least two DNS servers hosting each zone to provide fault tolerance for name resolution.

DNS servers and zones don't map one-to-one. In fact:

• One DNS server can manage one or more zones for efficiency and delegating administration of subdomains.

• One zone can be stored on one or more DNS servers for fault tolerance and load balancing.

It is generally best to have at least one secondary name server per zone. This way, if the primary name server for the zone goes offline, clients can still resolve names .

Standard zone files are stored in %SystemRoot%\System32\dns as a file with a .dns extension. For example, the forward-lookup zone for the mtit.com domain would, by default, be stored in the zone file mtit.com.dns .

Resolvers

You can stop or start the DNS Client service on a WS2003/2000/XP computer with net stop " dns client " or net start " dns client ".

Stopping the DNS client also flushes the resolver cache.

Resolvers can query both remote name servers and the local computer if it is running the DNS Server service.

Troubleshooting

To troubleshoot DNS server problems, you can use:

• nslookup , which can be used to issue DNS queries and examine zone files on local and remote servers.

• ipconfig , which can be used to view and flush the resolver cache and force dynamic updates by WS2003 clients.

• Event Viewer, which manages the DNS server log.

• The optional DNS log %SystemRoot%\System32\Dns\Dns.log , which keeps track of DNS server activity. This log is enabled and configured by:

Right click on DNS server Properties Logging select logging options

• The DNS console to monitor the DNS server by:

Right-click on DNS server Properties Monitoring select a test

Here is a basic troubleshooting procedure for checking a DNS server if problems occur (stop at the step where the problem is resolved):

1. Check Event Viewer first.

2. Go to the client and try pinging the DNS server to test for basic network connectivity.

3. At the client, open a command prompt and type nslookup 127.0.0.1 . If you get the name of the client in response to this, your server is OK. If it gives "Server failure" as a response, the server may simply be too busy (or the reverse-lookup zone in which the client's PTR record exists may be paused check the General tab of the properties sheet for this zone on the server).

4. If the response is "Request to server timed out" or "No response from server," then go to the server, open a command prompt, and type net start dns . If DNS is already started, then check the Interfaces tab on the properties sheet of the server to make sure that the server is listening on the interface to which the client's subnet is connected.

If a client queries a DNS server and receives incorrect information (wrong IP address for the queried FQDN), then you can troubleshoot the problem like this:

1. Go to the client and flush the resolver cache by typing ipconfig /flushdns at a command prompt.

2. Type nslookup IPaddresstoresolve IPaddressofserver . If you get a correct response, the problem was a stale cache entry. If not, the zone information on your authoritative name servers is in error. If you were querying the primary name server (or if your DNS is integrated with Active Directory), check the resource records for your host and whether dynamic update is configured properly on the client. If you were querying a secondary name server, check if zone transfers are configured properly as well.

See Also

Active Directory , DHCP , nslookup