Multiple Web sites can be hosted through a single IP address and port combination in two ways:
Multiple Web Servers Through a Single IP Address and Port: This requires that each DNS name in the Web server accelerator definition is unique and that none of the Web servers uses SSL. (See Configuration Considerations When Using Appliance Multihoming Features.) To do this, you simply configure Excelerator with a Web accelerator for each DNS name.
Multihomed Web Servers: You can also accelerate multihomed Web servers, which are Web servers that host multiple virtual Web servers with different DNS identities.
The following sections contain simplified examples for each scenario.
A company named Server Consolidation, Inc., offers acceleration services to several small companies, each of which has its own Web server. Server Consolidation knows that it can provide enough bandwidth to handle the combined Web traffic on one IP address, 30.1.1.1.
Server Consolidation installs an appliance and configures it with multiple Web server accelerators that each use the same IP address, 30.1.1.1, and fill from different Web servers.
Each company then arranges to have its DNS name (or names) resolve to 30.1.1.1.
After the DNS changes are complete, Server Consolidation's appliance is accelerating multiple Web servers through IP address 30.1.1.1.
Because Excelerator uses the DNS name to determine which Web server to fill a request from, one accelerator definition is required for each DNS name accelerated by the appliance.
NOTE: In this example, none of the Web servers could use SSL. See Configuration Considerations When Using Appliance Multihoming Features for more information.
A company named Web Host, Inc., provides hosting services for 50 different companies on a single Web server with an address of 10.1.1.1.
DNS resolves browser requests to each of the 50 DNS names to the same IP address, 10.1.1.1. The Web server routes each request to the appropriate area on its hard disks, based on the DNS name in the request.
Web Host decides to accelerate its Web server and installs an appliance. The company assigns 10.1.1.1 to the appliance and 10.1.1.2 to the origin Web server. It then defines an accelerator service on 10.1.1.1 that fills from 10.1.1.2.
DNS resolves requests to each of the 50 Web sites to 10.1.1.1 just as before, but the appliance now receives and services the requests, obtaining uncached objects from the origin Web server when necessary.
Because the appliance has only one accelerator defined on 10.1.1.1 and it is accelerating a single Web server on that address, it does not need the DNS name to resolve requests.
IMPORTANT: When an IP address is used for accelerating a single Web server, you need only one Web server acceleration service, even if the server is a multihomed server servicing browser requests to multiple DNS names.
However, if you configure Excelerator to accelerate more than one Web server on any given IP address, you must create a separate accelerator service for each DNS name that might appear in browser requests, including all the DNS names used on any multihomed servers.
We recommend you avoid the overhead of creating multiple accelerator services for a multihomed server by ensuring that its accelerator service has a dedicated IP address and port combination---one that is not used by another accelerator service.