Microsoft Web proxy event 14120 for every Web request

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This article was previously published under Q288236

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SYMPTOMS

If you install Microsoft Internet Security and Acceleration (ISA) Server 2000 in Integrated mode on a computer with only one network interface card, the following event may be logged for each Web Proxy request:

Event Type: Error
Event Source: Microsoft Web Proxy
Event Category: None
Event ID: 14120
Date: 01/02/2001
Time: 11:28:50
User: N/A
Computer: SERVERNAME
Description:
The ISA Server services cannot create a packet filter 157.54.12.183. This event occurs when there is a conflict between the Local Address Table (LAT) configuration and the Windows 2000 routing table. Check the routing table and the LAT to find the source of the conflict.
Data:
0000: 15 00 00 00 ....

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CAUSE

ISA generates a dynamic packet filter for every outgoing connection object so it can listen to the reply from the requested web server. On a machine with only one interface this will fail as it is not possible to do packet filtering.

Installing ISA Server in Integrated or Firewall mode requires a minimum of two network interface cards (NICs) for the packet filtering and Network Address Translation to work properly. This can either be two NICs or one NIC and one dial-up adapter. If you install ISA server in Integrated mode on a computer with only one network interface, ISA Server may log an event 14120 for each Web Proxy request.

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RESOLUTION

Installing ISA Server in Integrated or Firewall mode on a computer with only one network interface is not supported. To resolve this problem, uninstall ISA Server and install it in Cache mode or add an additional network interface.

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