Site clustering refers to hosting multiple websites or applications on one host, while multi-IP server means that the server provider assigns multiple independent IP addresses to each site. The main reasons why a site group uses multiple IP servers are as follows:

　　Improve SEO effect:

　　Each IP address can be viewed by search engines as an independent website, which helps improve search engine optimization (SEO) results. When search engines crawl a website, they treat each IP address as a separate entity, which allows the site to appear independently in search results.

　　Avoid IP bans:

　　If you host multiple websites on the same IP address, and one of the websites is blocked or has security issues, it may cause the entire IP address to be blocked, thus affecting the normal access of other sites. Using a multi-IP server can prevent this from happening because each site has an independent IP address and problems with one site will not affect other sites.

　　Distribute traffic and load:

　　Using multiple IP servers can spread traffic to different IP addresses, thereby reducing the load pressure on a single IP address. This helps improve the performance and stability of the site, ensuring users can access the site quickly and enjoy a good user experience.

　　Independent SSL certificate:

　　If you need to use independent SSL certificates for each site (for example, each site uses its own domain name), then multiple IP servers are necessary. Each IP address can be associated with an independent SSL certificate, ensuring each site is able to use HTTPS encrypted connections.

　　It should be noted that using multiple IP servers also requires consideration of factors such as resource management, network configuration, and security. Make sure you choose a reliable service provider and properly plan and manage resource allocation for each site.