This is the /etc/pxe.conf file we used on our
pxe server. 

This is based on the example configuration that
ships with 6.1. 

Note that it points to entries in /tftpboot/X86PC/UNDI/$whatever
I really dont know the reasoning behind the  X86PC/UNDI bit,
but its how the default config had it setup. 

This setup will default to booting with bpbatch, though
it includes options for pxelinux, and the standard
intel pxe net loader. 

Documentation on changing the defaults are in the /usr/doc/pxe*/README
included with the pxe packages.