Multiple IP Addresses Cause Dynamic Packet Filter to Fail

Dynamic packet filters may fail to open and allow ANY traffic to pass to or from Microsoft Proxy Server version 2.0. The packet filter driver will still filter Internet requests; however, it will not allow data to pass into or out from the Proxy Server.

Enabling packet filtering and having more than one IP address bound to the external network interface of the Proxy Server causes this problem. Internally there was a problem with the member computation and the address check routine.

This problem is resolved in Microsoft Proxy Server 2.0 Service Pack 1 (SP1). For more information about Service Pack 1, please see the following article in the Microsoft Knowledge Base:

To work around this problem, remove the extra IP addresses from the external network interface of the Proxy Server. If more than one IP address is required, up to two additional external network cards can be installed. The Proxy Server 2.0 packet filter can support a maximum of three external network adapters.

Microsoft has confirmed this to be a problem in Proxy Server 2.0