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You are using a Microsoft Windows Server 2003 Service Pack 2 (SP2)-based multiprocessor computer that is running Microsoft Internet Security and Acceleration (ISA) Server 2006 or Microsoft ISA Server 2004. With this configuration, you experience the following symptoms:
CPU use for a particular processor reaches 100 percent.
The total throughput of ISA Server is greatly reduced or completely blocked.
Latency increases significantly even though other processors are used at much reduced levels.
Note This problem occurs only on multiprocessor computers that use a 32-bit operating system.
This problem occurs because of the "lazy Interrupt Request Level" (IRQL) handler that is included in Windows Server 2003 SP2.
To resolve this problem, use the Interrupt-Affinity tool to assign the interrupts of different network adapters to different processors. To do this, follow these steps:
Download and then install the Windows Server 2003 Resource Kit tools.
For more information about how to download the Windows Server 2003 Resource Kit tools, visit the following Microsoft Web site:
For more information about how to install the Interrupt-Affinity tool, click the following article number to view the article in the Microsoft Knowledge Base:
252867 How to install and use the Interrupt-Affinity Filter tool
Run the Interrupt-Affinity Filter tool.
Locate all the network adapters.
Use the following rules to assign a processor to each network adapter:
If the number of processors is large or if the number of processors is equal to the number of network adapters, assign a single, unique processor to each network adapter.
If the number of processors is less than the number of network adapters, use the \Network Interface(*)\Packets Received/sec performance counter to determine which network adapters have the highest values during high CPU use. Assign each of these network adapters a separate processor, and then assign the remaining network adapters in a round robin order.
Monitor the performance counters for twenty-four hours to make sure that the problem is resolved.
To verify that you are experiencing this problem, use one of the following methods.
Copy and then paste the following code into a new Notepad file. Then, save the file as “Counters.txt."
\ISA Server Firewall Packet Engine\*\ISA Server Web Proxy\*\PhysicalDisk(*)\*\Processor(*)\*\Memory\*\System\*\Network Interface(*)\*