I have tried the following pxelinux.cfg file.But don't know why the ip is not set and how to get the IP info appended then use ifconfig to set the IP.
Need emergency. thanks a lot.

display logo
label linux
kernel vmlinuz
append initrd=initrd.img vga=0x0314 ip=192.168.0.249:192.168.0.2:0.0.0.0:255.255.255.0::ff
ipappend 1

or

display logo
label linux
kernel vmlinuz
append initrd=initrd.img vga=0x0314 ip=192.168.0.249:192.168.0.2:0.0.0.0:255.255.255.0::eth0ff
ipappend 1

but after linux boot the ip is not set.

thanks a lot.