The minimum system requirements for Microsoft ISA Server 2006 are described in ISA Server EE Installation Requirements earlier in this document. However, for improved performance, plan the ISA Server 2006 hardware and Internet connectivity to meet the expected load. When determining the hardware required for an ISA Server computer, consider the following questions:

The answers to these questions depend upon your specific security configuration needs and on the deployment scenario. Specifically, all of the following impact the hardware recommendations: the firewall policy configuration, logging requirements, peak total network throughput, and whether you are publishing servers or simply allowing Internet access. Of these, peak total throughput on the Internet connection has proven to be the most significant factor in determining computing needs, because in most cases, it represents the Internet capacity needs.

The following table provides general guidelines, depending on the Internet link bandwidth you use. Note that the recommendations listed here assume Web traffic and a policy configuration with several hundred rules. The recommendations also assume no special configurations such as caching or third-party filters. If you enable caching, an Internet link with 20 to 30 percent lower bandwidth may suffice. Furthermore, if you configure the clients to be proxy-aware, you can expect double throughput for the same hardware configurations.

Internet link bandwidth Up to 7.5 megabits per second (Mbps), or 5 T1 Up to 25 Mbps Up to 45 Mbps, or T3 Notes





Processor type

Pentium III 550 MHz (or higher)

Pentium 4 2.0–3.0 GHz

Xeon 2.0–3.0 GHz

Alternatively, you can use other processors with comparable power that emulate the IA-32 instruction set.In deployments requiring only stateful inspection filtering (no need for higher application level filtering), the Pentium 4 and Xeon processor recommendations reach LAN wire speeds.


256 MB

512 MB

1 gigabyte (GB)

With Web caching enabled, these requirements may be higher.

Disk space

150 MB

2.5 GB

5 GB

This is exclusive of hard disk space you need to use for logging.

Network adapter

10/100 Mbps

10/100 Mbps

100/1000 Mbps

These are the requirements for the network adapters not connected to the Internet.

For more detailed information, see "Best Practices for Performance in ISA Server" at the Microsoft TechNet Web site.