Ignoring DHCP settings

[Scotty]

G'day

I'm trying to put together a system which will enable us to disregard the settings for next-server and filename in DHCP as having to change that setting (which we can do even though we don't 'own' the DHCP server) is adding additional levels of complexity to our process.

After booting from IPXE and hitting Ctrl-P, then running dhcp I get the settings one would expect.

Editing those settings (either via config or using set commands) when I run

chain tftp://servername/pxelinux.0

it just times out.

However - when I get the next-server and filename settings in DHCP set to match the settings of the server and pxelinux.0 it works.

It seems that the existing settings from the DHCP server are still interfering.

The thread at

http://forum.ipxe.org/showthread.php?mod...85#pid4285

seems to address the same issue ... however I wasn't able to follow the suggested solution.

Any ideas?

Scotty

[mcb30]

(2015-05-06 02:53)Scotty Wrote:  Editing those settings (either via config or using set commands) when I run

chain tftp://servername/pxelinux.0

it just times out.

However - when I get the next-server and filename settings in DHCP set to match the settings of the server and pxelinux.0 it works.

It seems that the existing settings from the DHCP server are still interfering.

In which scope are you editing the settings? The reconstructed DHCP packets passed to pxelinux.0 (or to any other PXE NBP) give priority to netdevice-specific settings, since the PXE API is implicitly requesting the DHCP packet for a single network device. This means that a setting in the "net0" scope will take priority over a setting in the top-level scope.

You probably want to do something like:

Code:

#!ipxe
dhcp
set netX/next-server 192.168.0.1
set netX/filename bootfile
chain tftp://${next-server}/pxelinux.0

Michael

[Scotty]

(2015-05-06 13:45)mcb30 Wrote:  In which scope are you editing the settings? The reconstructed DHCP packets passed to pxelinux.0 (or to any other PXE NBP) give priority to netdevice-specific settings, since the PXE API is implicitly requesting the DHCP packet for a single network device. This means that a setting in the "net0" scope will take priority over a setting in the top-level scope.

You probably want to do something like:

Code:

#!ipxe
dhcp
set netX/next-server 192.168.0.1
set netX/filename bootfile
chain tftp://${next-server}/pxelinux.0

Michael

Ah! I should have thought of that.

I'll give it a shot later today and update with my results

Post testing:

It worked as described ... dhcp set the details for net0, and manually setting the details for net0 let me override the dhcp supplied values.

Many thanks mate


Scotty