RE: ISA Publish Scenario
- From: "Thomas W Shinder" <tshinder@xxxxxxxxxxx>
- To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
- Date: Mon, 9 Aug 2004 19:47:54 -0500
Hi William,
The answer is *always* to create a split DNS. The ISA firewall really
doesn't like looping back through itself for requests from Internal
network clients. As you're noticed, when SecureNAT clients try to loop
back through the ISA firewall, it doesn't work because the ISA firewall
isn't proxying the request. It will work at times with the Firewall
client (since its acting as a Winsock proxy) and will always work with
the Web Proxy client.
Also, the ISA firewall doesn't have an integrated mode. You also get all
firewall features with the ISA firewall, although you can cripple it by
installing it in single NIC mode.
HTH,
Tom
-----Original Message-----
From: William Holmes [mailto:wtholmes@xxxxxxxxxxxxxx]
Sent: Monday, August 09, 2004 7:25 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] ISA Publish Scenario
http://www.ISAserver.org
Hello,
I am setting up ISA 2004 to publish several web servers. I have a
diagram at:
http://www.cs.cornell.edu/~wtholmes/publishingsetup.htm
With this setup there is a split routing problem and I was wondering if
there is a way to fix this within ISA.
The external listener on the ISA server is on the DMZ network. When a
web request comes into this listener from an external client everything
works as expected. The request goes through the Checkpoint firewall to
the DMZ to the ISA server which requests the page from the appropriate
back-end web server.
However when the request comes from an internal client it passes through
the checkpoint firewall to the ISA server which responds its internal
interface.
This creates a split route. The checkpoint firewall seeing the incoming
request but never seeing the outgoing request drops the connection. The
ISA server sees a request coming to its external interface from a subnet
that should only appear on its internal interface and also drops the
connection.
Solutions not involving ISA:
1. Create a split DNS so that requests for
http://isaserver_listener_address from an internal host are directed to
the internal network interface on the ISA server.
2. Modify the routing tables in the CISCO router to redirect requests to
the DMZ listener's address on the ISA server to the internal ISA server
address.
3. Configure all clients to use the ISA server as their web proxy.
My question: Is there a way to configure ISA so that requests received
on its external interface are answered on its external interface
regardless of the source IP. In other words when publishing a web site
can you ignore normal IP routing.
The answer is likely a no but I just thought I would ask.
Thanks
Bill
William Holmes (MCP)
Department of Computer Science
310 Upson Hall
Cornell University
Ithaca, NY 14853
wtholmes@xxxxxxxxxxxxxx
607 255-1757 (o) 607 227-6049 (c)
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