RE: ISA Publish Scenario
- From: "William Holmes" <wtholmes@xxxxxxxxxxxxxx>
- To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
- Date: Mon, 9 Aug 2004 21:00:55 -0400
Hello Tom,
The next question is does Microsoft intend to support a DNS server that
handles a split DNS environment? That is similar to views that are available
in Bind 9. When a request is made from an internal host you should get one
set of information. When the request comes from an external address you
should get another.
In our environment we are not primary on our dns so its quite difficult to
set up a split DNS. I could change the zone file after receiving it from the
primary name server but that's quite ugly.
Thanks
Bill
-----Original Message-----
From: Thomas W Shinder [mailto:tshinder@xxxxxxxxxxx]
Sent: Monday, August 09, 2004 8:48 PM
To: [ISAserver.org Discussion List]
Subject: [isalist] RE: ISA Publish Scenario
http://www.ISAserver.org
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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