Microsoft KB Archive/170251

= Filtering by Specific IP Addresses May Not Be Effective =

Article ID: 170251

Article Last Modified on 8/11/1999

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APPLIES TO


 * Microsoft Proxy Server 1.0 Standard Edition
 * Microsoft Proxy Server 2.0 Standard Edition

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This article was previously published under Q170251



SYMPTOMS
Enable filtering for Web Proxy and Winsock Proxy services by specified IP address may not work effectively.



CAUSE
Filtering by specified IP address may not work effectively because several IP address may answer for a given domain name. If you pick one address, you will miss the other addresses that mirror the same server content.

Also in some networks, IP addresses may be dynamically assigned by using Bootstrap Protocol (BOOTP) or Dynamic Host Control Protocol (DHCP) services. When BOOTP and DHCP are in use, the remote server's IP address may change.



WORKAROUND
Apply filtering based on DNS Domain names for specific sites.



MORE INFORMATION
If you manage a large private network that uses TCP/IP but does not connect to the Internet, you may find it easier to precisely filter access by entering specific IP addresses.

Although DNS filtering is easier to manage and generally preferred where available, listing individual IP addresses for filtering is a valid option where DNS naming services are not managed on your network, and your private network uses static IP addressing.

Additional query words: prx

Keywords: kbother KB170251

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