I had to check my DHCP configuration for a Dell Wyse Thin Client. But when you configure specific options like 161 and 162 you don’t see that options in a Wireshark capture during a Windows DHCP request.
Luckily for us CyberShadow created a great tool to test some specific DHCP settings an he even make it open source: https://github.com/CyberShadow/dhcptest
This DHCP tool have 2 great features:
- You can do a request for specific DHCP option
- You can send a vendor class so in my case I can pretend to be a Wyse Thin client.
DHCP Request Option
This will only work when you have configured Global DHCP settings.
dhcptest.exe --query --request 161
DHCP Vendor Class
First I had to figure what the vendor class was. I checked this on the DHCP server:
Or on a Thin client itself:
Then run this command:
dhcptest.exe --query --option "60=wyse-1000"
And you will get Vendor Specific Information in Hex.
You can do different things to translate the Hex into readable data.
- Compile the open source yourself yourself and create a output in a string
- Use a (online) hex convertor
- Open wireshark during the capture. Wireshark will translate this for you 🙂
Compile the tool
- Download the git repo
git clone https://github.com/CyberShadow/dhcptest.git
- Edit the file (add these 2 lines)
161 : DHCPOptionSpec("File Server", OptionFormat.str), 162 : DHCPOptionSpec("Root Path to the File Server", OptionFormat.str),
- Download DMD for Windows: https://dlang.org/download.html
- Install the DMD compiler
- Compile the dhcptest tool
This will create a exe for you and will translate the Hex to readable format.