[libvirt] Are there interfaces to change IP address of given domain before it runn

Dear all, I has created a image file in local filesystem. And now, I wrote a program based on libvirt to run two instances of given image file. But I found they are using the same IP address which make them cut off the network. So, I wonder there are any solution to guarantee that both VM instances would be given different IP address after they are started. Thanks in advance, Ian