Steps to changing the core domain of a WordPress multisite network:
1. Load and run Interconnect’s “Search and Replace” (DATABASE SEARCH AND REPLACE SCRIPT IN PHP, NOT THE PLUGIN) replacing the old domain with the new. It will change the following tables…
wp_options: options named “siteurl” and “home”
wp_sitemeta: the option named “siteurl”
wp_blogs: any entries in the “domains” column that have the old domain name
wp_id#_options: where each sub-site id# will have an options table, the “siteurl” and “home” settings will get updated with the new domain.
2. Change DOMAIN_CURRENT_SITE to the new domain in wp-config.php
3. For subdomain networks, be sure the new domain contains a wildcard subdomain record and consider adding subdomains to your DNS for each subdomain website.
4. If any site is not displaying, Network Admin -> Sites -> All Sites -> check site urls under Info tab and Settings tab for each domain and check your DNS. It can take time for the DNS changes to propagate throughout the internet.