[ipxe-devel] [gPXE] what is gpxe-encap-opts option used for?

[Michael Brown]

On Friday 10 Feb 2012 19:21:34 Ledochowski, Roy wrote:
> Hi all-
> 
> New member here.  Can anyone out there explain or point me to an
> explanation of what gPXE uses
> 
> option gpxe-encap-opts code 175 = encapsulate gpxe;
> 
> for?  In our packet sniffs we see gPXE requesting it, but we don't
> understand what it does and our IP new mgmt app (infoblox) doesn't have a
> direct way to configure the option, so I'm trying to understand how hard
> to push them to enable a way to set it.
> 
> Any help or pointers would be greatly appreciate.  Thx ahead of time

They're encapsulated options.  For example, an option 175 consisting of:

  175,4,1,1,3,255

would be interpreted as:

  175 - iPXE encapsulated options field
  4 - total length is 4 bytes
  1 - sub-option 1 (ipxe.priority)
  1 - sub-option length is 1 byte
  3 - value of ipxe.priority is 3
  255 - end of encapsulated options

See http://ipxe.org/howto/dhcpd#ipxe-specific_options for a current list of 
possible options.

Michael