Overview - DHCP Scope Options

If you are not using IP helpers to control the PXE process, you need to make some changes to your DHCP infrastructure to allow PXE booting to work. The DHCP server must be configured to enable it to reply to a requesting client with enough information to allow the client to obtain a boot file. This includes the IP Address of the PXE Server, the appropriate boot file name (according to client hardware type) and the URL and Port number for the https session.

• You need to define the IP of the server to do the initial download from, using filename (DHCP Scope Option 66).

• You need to define the appropriate filename to boot. This is unique per hardware type and needs to be defined through a rule or other DHCP server logic (DHCP Scope Option 67).

• We need to define the HTTPS url and Port for iPXE to use when communicating with the 2PXE Service. As we are using HTTPS this string needs to exactly match the host header of the machine, otherwise the TLS session will fail (DHCP Scope Option 175).

NOTE: To reiterate – “this needs to match the host header of the machine” this means it must be in lower case, must be spelt correctly and must contain a trailing slash:

https://<server.f.q.d.n>:<port>/

The following table shows what you need to set to make sure 2PXE works as it should and example values:

DHCP Name Field	Microsoft Name	Value	Example
Next-Server (SIADDRR)	Option 66	IP of the 2PXE server	192.168.10.30
Filename (Option 67)	Option 67	Boot file name	Unique per HW type BIOS both x64 and x86 Boot\x86\undionly.kpxe UEFI – x64 Boot\x64\snponly_x64.efi EUFI – x86 Boot\x86\snponly_x86.efi
Option 175	Option 175	URL of 2PXE FQDN in lowercase and port number	https://pxe01.2pint.local:8050/ Note: This needs to be lowercase and must contain the port and end with a slash “/”
Option 60	Option 60	PXEClient	PXEClient