If I try to use the hostname of the host to add:

[root@falcon tfox]# pxeboot -a -e eth0 -O rhel-3-as -r 10000 ijin.devel.redhat.com
invalid literal for int(): ijin

But, if I use the IP address for that same machine, it works:

[root@falcon tfox]# pxeboot -a -e eth0 -O rhel-3-as -r 10000 172.16.56.53
default rhel-3-as
 
label rhel-3-as
    kernel rhel-3-as/vmlinuz
    append initrd=rhel-3-as/initrd.img  ramdisk_size=10000

If you don't want to allow hostnames, it should at least give a better error
messages.