Network Configuration of WordPress CMS server

We wish to create a wordpress hierarchical CMS for an institute. Now when change the IP we need to reinstall the server again. How can one change the IP manually so that the site gets relocated? Also if we need to host a wordpress server onto an internal IP (behind a firewall : Iptable) having multisite option on. What changes shall be required for configuring this server?
Thanks and advance
-Gaur