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Problem

You want to enable DNS debug logging to troubleshoot issues related to DNS queries or updates.

Solution

Using a graphical user interface

Using a command-line interface

Use the following four commands to enable debug logging. For the log level, you have to add together the event codes you want logged and specify the result in hex. The available event codes can be found in Table 14-3.

	> dnscmd <ServerName> /Config /LogLevel <EventFlagSumInHex>

Use the following command to specify the location of the logfile:

	> dnscmd <ServerName> /Config /LogFilePath <DirectoryAndFilePath>

Use the following command to log only entries that pertain to certain IP addresses:

	> dnscmd <ServerName> /Config /LogIPFilterList <IPAddress1>[,<IPAddress2>…]

Use the following command to specify the maximum logfile size:

	> dnscmd <ServerName> /Config /LogFileMaxSize <NumberOfBytesInHex>

Use the following command to disable debug logging:

	> dnscmd <ServerName> /Config /LogLevel 0

Using VBScript

	' This code enables  
DNS debug logging.
	' ------ SCRIPT CONFIGURATION -------
	strServer = "<ServerName>" ' e.g. dc1
	' The log level must be in decimal, not hex like dnscmd
	intLogLevel = <EventFlagSumInDecimal> ' e.g. 65535
	arrFilterList = Array("<IPAddress1>") ' e.g. 192.168.1.12
	strFilePath = <DirectoryAndFilePath> ' e.g. c:\dnslog.txt
	intFileSize = <NumberOfBytesInDecimal> ' e.g. 50000000
	' ------ END CONFIGURATION ---------

	set objDNS = GetObject("winMgmts:\\" & strServer & "\root\MicrosoftDNS")
	set objDNSServer = objDNS.Get("MicrosoftDNS_Server.Name="".""")
	objDNSServer.LogLevel = intLogLevel
	objDNSServer.LogIPFilterList = arrFilterList

	 
objDNSServer. 
LogFilePath = strFilePath
	objDNSServer.LogFileMaxSize = intFileSize
	objDNSServer.Put_
	WScript.Echo "Enabled DNS  
Debug Logging on " & strServer

	' To disable  
debug logging, set the intLogLevel variable to 0

Discussion

With the DNS Server debug log, you can record all DNS operations received and initiated by the server, including queries, updates, zone transfers, etc. If you need to troubleshoot a particular host, you can use the LogIPFilterList setting in dnscmd or the WMI DNS Provider to restrict the log to operations performed only for or by that host.

The most important debug log setting is the log level. With the DNS snap-in, you can select from a list of available options. With Windows Server 2003, the DNS snap-in provides an intuitive interface for selecting the required options. On Windows 2000, you are presented with a list of checkboxes and you have to figure out which ones need to be used in conjunction with one another. You have a similar issue with CLI and VBScript solutions, where you need to determine what log level you want to set.

Table contains all of the event codes with their hexadecimal and decimal values.

Table . DNS debug logging event codes

Hexadecimal value	Decimal value	Descriptions
0x0	0	No logging. This is the default.
0x1	1	Query transactions.
0x10	16	Notifications transactions.
0x20	32	Update transactions.
0xFE	254	Nonquery transactions.
0x100	256	Question packets.
0x200	512	Answer packets.
0x1000	4096	Send packets.
0x2000	8192	Receive packets.
0x4000	16384	UDP packets.
0x8000	32768	TCP packets.
0xFFFF	65535	All packets.
0x10000	65536	AD write transactions.
0x20000	131072	AD update transactions.
0x1000000	16777216	Full packets.
0x80000000	2147483648	Write-through transactions.

DNS debug logging can come in handy if you want to look at the dynamic update requests a particular DNS Server is processing. For example, if a client or DHCP server is attempting to dynamically register records, you can enable the Update Transactions log category on the DNS Server you think should be processing the updates. If you don’t see any update transactions, this can indicate that another server is processing the dynamic update requests.