Problem with Caching and NAT in ISA2006

Friday, June 19, 2009 5:52 AMFaraz Jamil

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Hi Everybody,

Im Faraz from Pakistan, a telecom engineer by profession.

Actually these days im stuck with a problem while deploying ISA2006 Enterprise Edition into my network. My basic purpose is to deploy ISA2006 for web traffic content caching. Now i have installed and configured ISA2006 Enterprise Edition and its working fine as per my design requirements but the only problem is it is changing the source IP of my web traffic even though i have configured it for simple routing purpose.

Let me explain the scenario in some detail for your convinience... the network topology is as follows;

Firewall------> ISA2006------->Router-------> internet

Note: We are performing NAT on firewall instread of my ISA or Router.

Please note that whenever a user tries to browse internet like SIP: 10.x.x.x DIP (any URL say http://www.Yahoo.com) the traffic reaches at Firewall and then Firewall NAT this traffic to a public IP.... so the SIP then becomes a public IP say 203.x.x.x and DIP remains the same...

Now when this traffic passes through ISA2006, by default ISA2006 again NAT this traffic to another public IP assigned to its external NIC... now when traffic comes out of ISA2006 external NIC the SIP changes to x.x.x.x (public IP assigned to external interface)...

I have tried a solution to avoid this ISA NAT... i disabled web proxy filter for HTTP protocol it solved my purpose but at the same time it created a new problem... i noticed that the Cache Functionality of ISA was also stopped.

When i enable Web Proxy Filter for HTTP, NAT by ISA gets started and Cache resumed.

Kindly advise your expert opinio how can i get rid of this problem... I just want to simply route & cache my traffic through ISA2006 server without any NAT by ISA. Please note that i have already selected Routing Mode.

BR// Faraz Jamil