Question

How to setup ISA 2006 with two NICs

Asked by: Moey_G

Hi All Experts,

I am not familiar with ISA 2006 and in need of some help. One of my clients is deciding on ditching their hardware firewall due to restrictions and want to implement ISA 2006 as their software firewall.

The server which will host ISA 2006 is Windows 2003 std and contains 3 NICs. I am not sure if I should use all 3 or just use 2 of them , but they do have a web server and exchange 2003 which can be placed in a DMZ if all 3 NICs are being used.

My problem is I dont know how to configure the server as I have never done this before . I also dont know if I should use the 2 NICs or 3 NICs ? I am not entirely sure how to configure the internal NICs and External NICs as well ? I have been given an IP address from the ISP to use on the external NIC , but would appreciate if someone can give me some guidance and recommendations.

Moey_G

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Asked On
2009-08-27 at 04:08:40ID24686111
Tags

ISA 2006

Topics

MS Forefront-ISA

,

Network Cards & Adapters

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Answers

 

by: PaciBPosted on 2009-08-27 at 05:36:28ID: 25197224

Hi,

If you want to have a DMZ, then you absolutely need 3 NICs: One for internal network side, on for DMZ side and one for external side.

Start by install Windows 2003 and configure the NICs and IP layers...

There are some questions you must ask to yourself and answer and informations you must collect before proceeding :

1) Do you ISA server need to be member of a domain ? If yes, then your ISA server need to resolve internal DNS names AND external DNS names. That requires a specific DNS configuration

2) What are the IP ranges you use in your internal network, including all the branch office that may use this ISA server?

3) What is the IP range of your DMZ network?


If you have these informations, you should start by configuring IP on NICs before going on with ISA installation.

Give precise names to your NICs, avoid use of default names like "network connection #1" that Windows proposes after installation. Rename you NICs with names like "LAN", "DMZ and "External".
Start by configure the external NIC: give IP address and mask matching with what your ISP give to you. Configure IP gateway on this NIC. THE EXTERNAL NIC IS THE ONLY NIC THAT MUST HAVE A IP GATEWAY CONFIGURED! Don't configure DNS servers for now.
Configure your DMZ NIC: very simple, only IP address and mask.
Configure you internal NIC: IP address and mask only for now.

Then, if you internal network has several IP ranges you must create specific IP routes to explain your ISA server how to join these IP ranges.
As an example, if your internal NIC on ISA has to following parameters: IP address = 10.1.0.254, mask = 255.255.0.0 and if you have another internal network using ip range 10.2.x.x with mask 255.255.0.0 then you need to type the following command on ISA to add the ip route:
ROUTE ADD 10.2.0.0 MASK 255.255.0.0 w.x.y.z -P
(where w.x.y.z is the IP address of the internal routeur that allow you to reach the internal subnet 10.2.x.x, and -P means that this route must be permanent and will not disappear after a reboot).
Do like that for every internal IP subnet.

Make pings to some of the internal computers (using IP address because until now you have not DNS resolution) on every internal subnets to verify IP routing is ok.


Now about DNS, if your ISA server must not be member of a domain (ISA is standalone server) then go on IP configuration of the external NIC and configure external DNS addresses that your ISP gave to you.
If your ISA server must be member of internal domain then ISA must be able to resolve external DNS names to give access to Internet but also resolve internal names to locate domain controllers... For my part, in this situation, I install DNS service on ISA server and configure this DNS service with no DNS zone but only DNS forwarders: I use a conditional forwarder for Active Directory domain suffix "mydomain.local" and mention IP addresses of internal DNS servers, then I add a unconditional forwarder to external DNS servers. Finally, I configure all NICs to use 127.0.0.1 as DNS server.
Doing that, ISA server use its own DNS service to resolve any dns name. If the DNS suffix of the name matches with domain dns name then the conditional forwarder send the request to an internal DNS server, else it sends the request to the external DNS.

When you have done that, and have validated the DNS resolution by doing some ping on internal and external DNS names, you can join the domain (if your ISA need to be a member).

Then you can install ISA. It's easy. During installation, ISA server installation wizard will detect multiple NICs and will ask you for internal IP ranges. You must include all IP ranges that are not externals (meaning LAN and DMZ ip ranges). You can easily indicate these ranges by selecting all internal and DMZ NICs. ISA will automatically generate ip ranges by looking at NIC configuration and IP routes.

Have a good day.

 

by: Moey_GPosted on 2009-08-27 at 19:08:58ID: 25204495

Hi PaciB,

Thank you for the quick response and detail. The ISA Server is also going to be used as a proxy and the server will be on the domain as requested.

The LAN subnet is 10.0.0.x /24 - will connect to the local switch
The WAN subnet is x.x.x.x /30 - will connect directly to the SHDSL router

There is no subnet for the DMZ. If I were to create a subnet for the DMZ , where will this connect ?

If I was to publish OWA 2003 or other services , can this be done with 2 NICs ?

 

by: PaciBPosted on 2009-08-28 at 00:37:12ID: 25205589

Hi,

So until now you don't have a DMZ managed by ISA server. If you want to create one one day, you wil have add a third NIC on ISA server to connect to this DMZ.

So you only have 2 NICs, that's not a problem at all. From ISA point of view one of these NICs (the WAN NIC) must be considered as external... That means that the WAN subnet that exists between your ISA and the SHDSL routeur mustn't be declared in any network object in your ISA server. ISA will then automatically suppose that the WAN subnet is a part of the "external" unreliable network.


Yes you can publish OWA and other internal server with 2 NICs.

Finally, your ISA server will be a member of your internal domain, so it has to resolve internal DNS names to find controllers, but it will also be used as a proxy server, so it has to resolve external DNS names also...
You should then apply what I told you about DNS service on ISA using conditional forwarder to internal DNS and unconditional forwarder to external DNS.
You CAN NOT just indicate internal and external DNS servers to ISA on NICs IP configuration... This won't work. You must make things so that ISA request a DNS service that is able to resolve any name, whatever it is internal or external.

What I described about DNS service installed on ISA is one solution, it's the one I usually install for my customers, but it'is not the only one. You might prefer to make things so that your internal DNS can resolve internal and external names, and then configure ISA to interrogate these internal DNS... Do what you want as long as all the DNS servers you configure in IP configuration of your ISA server (on any NIC) is able to resolve external AND internal names.

Have a good day.



 

by: Moey_GPosted on 2009-08-29 at 20:52:07ID: 25216300

I will be applying the above early next week with the exception of using the current internal DNS server and adding the ISP DNS as a forwarder for external DNS resolutions.

Unfortunately the only way for me to test this is after hours as there is only one WAN connection available and the need to disconnect their existing firewall.

Will let you know how I go.

Many thanks for the advice.

 

by: Moey_GPosted on 2009-09-02 at 14:01:17ID: 25245661

I seem to be running into trouble with DNS.

On the WAN side , I have setup all the required IP given by the ISP.

ip address: x.x.x.x  ( ISP address )
subnet mask: x.x.x.x  ( ISP address )
default gateway: x.x.x.x  ( ISP address )

DNS : Blank

On the LAN side , I have setup

ip address : x.x.x.x
subnet mask: x.x.x.x
default gateway: blank

DNS: x.x.x.x  ( Internal DNS server ) which also has forwarders setup to the ISP DNS servers.

If I use the above configuration , I am unable to browse the internet. If I then remove the DNS settings from the LAN NIC and enter the ISP DNS servers on the WAN NIC , I am successfully able to browse the internet. I have not fully tested the ramifications of this setup , but need to see if this affects client machines.

 

by: PaciBPosted on 2009-09-10 at 02:37:25ID: 25298596

Hi,

Did you verify that internal DNS can join external DNS and that your ISA server can join internal DNS (you should have to create a rule for that).

You can use nslookup command to make DNS tests.

With the configuration that you use (ISA server using external DNS) your ISA server cannot join the internal domain... So if ISA is supposed to be a member of the domain this will malfunction.

Have de good day.

 

by: Moey_GPosted on 2009-09-10 at 16:52:44ID: 25305678

Hi ,

I found two things that were stopping me from this working correctly.

1. The ARP table on the router was still using the old MAC address , even though I had this cleared by the ISP .

2. The virus scanning software on the machine also had a built-in firewall that was stopping me from accessing the internet correctly as well.

Thanks for all your help. I am still going to give you the points for a detailed explanation and assistance.

Cheers.

20120131-EE-VQP-002

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