first of all, your client PC should have a netboot capable network card and about 512MB RAM, because the SystemRescueCd image will be loaded completely to RAM.
– setup a TFTP server which delivers the following files: pxelinux.0, rescuecd, initram.igz
– add a pxelinux.cfg file with the following content
APPEND initrd=initram.igz rootpass=1234 dodhcp setkmap=us video=ofonly vga=0 cdrom scandelay=5 netboot=http://192.168.1.1/sysrcd.dat
– setup a webserver which delivers the following file: sysrcd.dat
– setup netboot (look in your BIOS if this is supported)
– boot it
You’re done… as you can see, the client will automatically do dhcp and the root password for the ssh access will be set to 1234 :-)