On SLES 11 when boot from an ISO (Xenserver) how do I get an IP via DHCP during the install?

I am installing Suse 11 as a guest in Xenserver and I need to point it to my autoyast install.xml file. My intention was to use autoyast=http://webserver/install.xml but in order to do this I need to have an IP on my network. I can see on my DHCP server the guest when booting from the ISO is not grabbing an IP. If I let the installation complete without specifying an autoyast file the guest will grab an IP address from DHCP. So I believe my network is configured properly.