Ever wondered why you had to create a custom DHCP option (dhcp opt 60) with "PXEClient" in it in order to use PXE?
Well, you don't!
You have to create this dhcp option only if:
- You have a PXE Service that binds on UDP 4011 and that runs on the same host that also runs a dhcp service (bound on UDP 67)
- You need this PXE Service to provide the "network boot program" details to your PXE clients.
These details are actually: TFTP server IP address (DHCP option 66) and network boot program file name (DHCP option 67)
If you know these details, you can perfectly make the economy of a PXE Service. Just fill these dhcp options (66 and 67) with the needed data.
For instance, if your TFTP server runs on the host with IP address 192.168.1.10, and if your network boot program file name is pxelinux.0, just configure your dhcp server so that its option 66 is "192.168.1.10" and option 67 is "pxelinux.0".
No dhcp option 60, no "PXEClient".
Note that your DHCP server can also run on the same host (192.168.1.10 in this example)
Also, do not set this dhcp option 60 if you have a PXE Service running on an host that does not run any dhcp or bootp service.
The DHCP option 60, when set to "PXEClient" is used only to instruct the PXE clients to try to use a PXE Service bound on UDP port 4011. Actually, if there is a bootp or dhcp service bound on UDP port 67 of an host (usually called a server), a PXE service cannot bind on that port on that host. Since the PXE Service uses BOOTP/DHCP packets to send the options 66 and 67 to the clients, it needs to be able to bind to the associated port (bootps) or to an alternated port (4011) that the clients know they must use as the alternate port. And to instruct the clients to use this alternate port, you have to set dhcp option 60 to "PXEClient".
Well, you don't!
You have to create this dhcp option only if:
- You have a PXE Service that binds on UDP 4011 and that runs on the same host that also runs a dhcp service (bound on UDP 67)
- You need this PXE Service to provide the "network boot program" details to your PXE clients.
These details are actually: TFTP server IP address (DHCP option 66) and network boot program file name (DHCP option 67)
If you know these details, you can perfectly make the economy of a PXE Service. Just fill these dhcp options (66 and 67) with the needed data.
For instance, if your TFTP server runs on the host with IP address 192.168.1.10, and if your network boot program file name is pxelinux.0, just configure your dhcp server so that its option 66 is "192.168.1.10" and option 67 is "pxelinux.0".
No dhcp option 60, no "PXEClient".
Note that your DHCP server can also run on the same host (192.168.1.10 in this example)
Also, do not set this dhcp option 60 if you have a PXE Service running on an host that does not run any dhcp or bootp service.
The DHCP option 60, when set to "PXEClient" is used only to instruct the PXE clients to try to use a PXE Service bound on UDP port 4011. Actually, if there is a bootp or dhcp service bound on UDP port 67 of an host (usually called a server), a PXE service cannot bind on that port on that host. Since the PXE Service uses BOOTP/DHCP packets to send the options 66 and 67 to the clients, it needs to be able to bind to the associated port (bootps) or to an alternated port (4011) that the clients know they must use as the alternate port. And to instruct the clients to use this alternate port, you have to set dhcp option 60 to "PXEClient".
by: vivigatt on 2012-02-03 at 06:16:47ID: 41737
When using a PXEService, dhcp options 66 and 67 are sent to the PXE clients by the PXE service itself, not by DHCP service.