Limitations of Virtual Subhosting Virtual Subhosting is a great feature of our Virtual Private servers System. However, there are some limitations to this capability which you should understand. These limitation include the following: Virtual Subhosting is made possible by the introduction of HTTP/1.1. In order to view subhosted domains you must have a browser which is HTTP/1.1 compliant. Generally speaking, Virtual Subhosting is supported by Netscape Navigator 2.0+ and MSIE 3.0+. Any other browser that is HTTP/1.1 compliant will be able to access a subhosted domain. If your clients are using an older browser which is not HTTP/1.1 compliant they will not be able to view their sites, nor other sites which are using Virtual Subhosting. However, considering that together Netscape and MSIE have 90-95% of the market share, this is generally not major a problem. Nonetheless, it is good to be familiar with this limitation. A Virtual Private Servers is capable of handling 30,000 to 50,000 hits (assuming hits generally request about 5 kb of data) per day. That is not "visitors", rather hits or requests for files. For instance, if you have 5 Subhosted domain names, each which is trying to accommodate 10,000 hits per day (which really isn't that much if you have a graphically intensive page; one request for a .gif or .jpeg equals one hit!) there will likely be a problem. This "slowdown" will affect all of your clients on the Virtual Private Servers you are using to Subhost. When a slowdown occurs a wise user will properly "manage" his or her Virtual Private Servers by reducing the number of Subhosts on the Virtual Private Servers by either upgrading one of the especially high traffic Virtual hosted sites to its own Virtual Private Servers or by moving some Subhosts to a less busy Virtual Private Servers. Either way, proper load balancing is a science that a user must have a feel for in order to succeed with serious Virtual Subhosting. A Virtual Private Servers can only host a finite number of Virtual Subhosts due to performance reasons. Consider the following recommendations when deciding how many Subhosts to place on a single Virtual Private Servers. Server A: Server B: Server C: around  5 low volume subhosts around 25 low volume subhosts around 60 low volume subhosts We cannot guarantee the number of Virtual Subhosts you will be able to host since each site uses a different amount of resources. It may be that you can only host one other Virtual Subhost before resources are exhausted on your Virtual Private Servers. It is up to you to monitor Virtual Subhosts and upgrade high load Virtual Subhosts to their own Virtual Private servers. Virtual Subhosting obviously uses the resources of a single Virtual Private Servers to accommodate the needs of multiple web sites. Among the resources that are shared is the single IP address that is associated with the Virtual Private Servers. Search engine "spiders" which are not HTTP/1.1 compliant will not be able to index the sites. Most major spiders and search engines are now HTTP/1.1 compliant. A Virtual Private Servers can only support a single Digital Certificate. This can make the use of SSL difficult since all Subhosts must use the same Digital Certificate and only one domain name can be associated with a Digital Certificate. A Virtual Subhost does not have telnet access to the Virtual Private Servers. Microsoft® FrontPage® 97 child webs will not work within a Virtual Subhosting environment. (However, Microsoft® FrontPage® 98 child webs will work with Subhosting). There are some limitations to the e-mail capability of Subhosts, namely how the Virtual Private Servers interprets e-mail addresses. For instance, if you send an e-mail to "john@abc.com" and "john@xyz.com" the Virtual Private Servers will view these as the same address. This is because to the Virtual Private Servers, "john@abc.com" and "john@xyz.com" both resolve to "john@192.41.5.2" because both domain names resolve to the same IP address. However, we have developed a way to get around this limitation by using a proprietary utility titled "virtmaps". See our document, Providing E-Mail for Virtual Subhosts for more information. It is important to understand that giving cgi-bin access to your subhosted clients is a potential security risk. This is because the CGIs your customers upload and execute have all of the rights and privileges of the CGIs you execute. Therefore, it is possible for a subhosted client, which has been granted CGI privileges, to read or remove any file in your directory hierarchy. Moreover, it is possible for a malicious Subhosted client to crack weak passwords and gain shell access to your Virtual Private Servers. see our document, Virtual Subhosting Security Issues for more information.