libvirt users - Sep 2014 - How to configure the container's NIC automatically with an assigned IP address

Dear all,
I want to run a TCP/IP application automatically after I start the container
using "virsh -c lxc:/// start mycontainer". Does anybody know how to
configure the NIC automatically with an assigned IP address? I couldn't find
useful information from domain XML format spec and it only talks how to set the
mac address (http://libvirt.org/formatdomain.html) .
Your response will be highly appreciated.
Cheng