Scenario: Deploying one accelerator for multiple Web or streaming servers

About this scenario

In this scenario, one accelerator is deployed for three Web servers or streaming servers.

Illustration of the scenario topology

The following illustration shows a single accelerator servicing multiple Web servers or streaming servers.

Overview of configuration steps

When you configure an accelerator to accelerate multiple Web servers or streaming servers, you take the following steps:

Configure the host name and IP address for the accelerator.
Configure IP address aliases and host name aliases for the interfaces on the accelerator. You might, for example, want to have one interface handle requests for one Web server or streaming server.
Configure the accelerator options and rules, which enable the accelerator to send cache misses to the correct Web server or streaming server.

Accelerator host names and IP addresses

Assume for this scenario that only one network card is installed in the accelerator but that there are multiple IP addresses associated with that card. Therefore, the accelerator needs IP address aliases assigned to the interfaces.

The following table shows the configuration of the host name, IP address, IP address aliases, and virtual host names on the accelerator.

Data to provide	Configuration data	Comments
Host name*	www.A.com*	In this example, the host name that was assigned to the Web servers or streaming server becomes the host name of the accelerator. The original Web server or streaming server is renamed. You can assign any names to the Web servers or streaming servers. However, Network Appliance recommends that you do not assign the same host name to both the accelerator and the Web server or streaming server because this might be a problem for DNS. Note Because a streaming MMS server is accessed by IP address only, the host name is not a critical setting on accelerators that service streaming MMS servers.
IP address*	IP address A	This is the IP address for the accelerator. When you need multiple IP addresses for the same interface, you need to assign IP address aliases. Doing so enables the accelerator to handle the requests for the multiple Web servers or streaming servers appropriately.
IP aliases (for IP addresses)	IP address B IP address C	In this example, a separate IP address alias is assigned to each interface on the accelerator. Use the IP Aliases option on the Network - Interfaces page to configure each IP address alias.
Virtual accelerator host names	www.B.com www.C.com	In this example, the IP alias addresses will handle requests for the second and third Web servers or streaming servers. A virtual accelerator host name associated with each IP alias must be assigned through DNS so that a particular IP alias address can handle requests for a particular Web server or streaming server. In this example, the Web servers or streaming servers are renamed, and the original names are used as the virtual accelerator host names. Note Because a streaming MMS server is accessed by IP address only, the virtual accelerator host name configured for the accelerator is not required to support streaming MMS acceleration.

If necessary, you can change the IP address (on the Network - Interfaces page) and the host name (on the System - Host Name page) in the Appliance Manager.

Acceleration rules for multiple servers

The following acceleration rules map requests to specific Web or streaming servers.

Accelerator				Web Server
IP	Port	Host	Path	IP/DNS Host	Port	Host	Path
IP_addr_A	*	www.A.com	*	www.internal.A.com	8080	*	*
IP_addr_B	*	www.B.com	*	www.internal.B.com	8080	*	*
IP_addr_c	*	www.C.com	*	www.internal.C.com	8080	*	*

The entries in these options map each Web server or streaming server to the accelerator or to a virtual accelerator host configured for this appliance.

The Web server's or streaming server's host name was www.A.com, but it was changed so that the accelerator could be assigned the host name.

How the appliance processes Web or streaming media requests

When a request is received by an accelerator, the accelerator first examines the IP address on which the request came in. Next, the accelerator examines the host name in the MIME header. The accelerator looks for a match of both the IP address and destination host name to determine the Web server or streaming server for which the request is intended. If the accelerator cannot match both the IP address and host name, it chooses the best possibility according to the IP address.