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How to: monitor Windows DNS servers for use of certain server names.

By Johan van Soest.

Published : 2014-06-02.

Last updated : 2020-11-15.

Of course one can use network sniffer software such as Wireshark or other tools¹ to monitor the DNS traffic for certain server name requests. The standard default debug logging of the DNS service can give a quick indication without installing additional software.

Steps

On the DNS server turn on Debug Logging (select properties on the DNS-Service) and set the following properties:
Windows 2012 r2 DNS server properties dialog showing the required Debug Logging options.
The default logfile can be found here: %systemroot%\System32\dns\Dns.log
The log contains entries in the format
- Date (month,day,year)
- Time
- Don't care
- Don't care
- Don't care
- UDP the protocol used
- Rcv it is a request to the DNS server
- Originating IP-address
- Don't care
- Q type is query
- [] Don't care
- Address type A => IPv4 AAAA => IPv6
- The requested domain with length denotifiers (PASCAL style)

5/31/2014 5:00:28 PM 1290 PACKET  0000000006F3D750 UDP Rcv 10.1.1.13      000a   Q [0001   D   NOERROR] A      (8)vansoest(2)it(0)

5/31/2014 5:00:28 PM 1290 PACKET  00000000070EEED0 UDP Rcv 10.1.1.13      000b   Q [0001   D   NOERROR] AAAA   (8)vansoest(2)it(0)

This example shows a DNS request from the system with ip-address 10.1.1.13 (can be IPv4 or IPv6 address format) requesting the ip-address for vansoest.it

Just filter the log on the server name you need (for example "vansoest") and you have a list of systems still referencing the server.
No reboot or restart of the DNS server and service required.

Footnote 1

Kevin Manning of Comparitech was so kind to report a broken link about Microsoft's Message Analyzer that is discontinued. On this site you can find an overview of packet sniffers

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