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Should Forefront  TMG be a member of my domain?

Posted on 2010-11-12
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Last Modified: 2012-05-10
I'm looking at setting up FTMG in a virtual environment and using it as my primary firewall (eliminating our sonicwall hardware appliance).  Should this VM be a part of my domain, or should it be compeltely standalone since it will have a direct connection to the internet?
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Question by:sbumpas
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by:Hisham_Elkouha
Hisham_Elkouha earned 25 total points
ID: 34124250
The ISA server cannot communicate users if it is not a member of the domain. But it would be more secure if you leave it workgroup, in this case you should create a rule that allow LDAP protocol between ISA and you domain controller.
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by:sbumpas
ID: 34124272
What communication would need to take place between users?  I was planning on using it as a L2/L3 firewall specifically (we do not have anybody connecting externally).
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by:Mohamed Khairy
ID: 34125014
You can configure Microsoft Forefront Threat Management Gateway as follows:

- In workgroup mode.

- As a member of an existing corporate domain.

- In a dedicated domain that has one-way or two-way trust with the corporate domain configuration.

There are a number of considerations when deciding whether to install in domain or workgroup mode:

When access rules require internal clients to authenticate for outbound access, Forefront TMG can authenticate domain user accounts against an Active Directory directory service domain controller. Web proxy requests in a workgroup environment can be authenticated against a RADIUS server.

Firewall client requests automatically include user credentials. To authenticate these requests, Forefront TMG should belong to a domain. In a workgroup environment, you can authenticate requests with user accounts that are mirrored to accounts stored in the local Security Accounts Manager (SAM) on the Forefront TMG server, but this requires some administrative overhead for secure management.

To authenticate inbound requests to internal Web servers using domain account credentials or certificate authentication, Forefront TMG must belong to a domain. In a workgroup environment, a RADIUS or SecurID server can be used for authentication.

To authenticate virtual private network (VPN) requests using domain account credentials or certificates, Forefront TMG must belong to a domain. In a workgroup environment, a RADIUS server can be used for authentication.

You can configure VPN client user mapping to map users of operating systems other than Microsoft Windows to domain user accounts. User mapping is only supported when Forefront TMG is installed in a domain.

In a domain, you can lock down the Forefront TMG server using Group Policy, rather than by configuring only a local policy.

In a domain environment, if Active Directory is compromised, for example by an internal attack, the firewall can also be compromised, because a user with Domain Administrator rights can administer every domain member, including the server running Forefront TMG. Similarly if the firewall is compromised, the domain in which Forefront TMG is located is also at risk. By default, the Domain Admins group is in the Administrators group on the Forefront TMG server.

You can use these article and refernces where you can find your planned deployment described as a commonly used scenario and Network topology considerations:

http://technet.microsoft.com/en-us/library/dd897048.aspx
http://technet.microsoft.com/en-us/library/cc995141.aspx
http://technet.microsoft.com/en-us/library/ee796231.aspx#kjdfg947jfht

Hope these links will help you understand the key features you will lose when you implement a workgroup model.

Regards,
MKhairy

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by:sbumpas
ID: 34125097
Thanks; from the reading material it looks like I'll be doing an edge configuration in a workgroup with ISP redundancy.  I will configure rules using subnets rather than users/groups (1/2 of my infrastructure is not ina domain).

Do you have any experience with this type of deployment?
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Mohamed Khairy earned 75 total points
ID: 34125899
Experience on what? deployments steps or guide lines?

Anyway, here is a the steps on hoe to enable Internet Service Provider (ISP) redundancy:

http://technet.microsoft.com/en-us/library/dd440984.aspx

Also you should make sure that b automatic metrics is turned off because if its not turned off so when the operating system recalculates the network selection, it may cause misalignment with Forefront TMG route cache functionality. This can interrupt communication, such as UDP communications used typically by Instant Messenger network discovery phase.

http://blogs.technet.com/b/isablog/archive/2009/10/14/the-isp-redundancy-feature-of-forefront-tmg.aspx

Hope this may helps and I am waiting for any other clarifications needed?

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by:Keith Alabaster
ID: 34128304
There is no question here. If you can add your ISA/TMG server to the domain then you should.
It is line with best practice, it gives you most flexibility, it less fiddlely in respect to configuration, you need to open less ports, it simplifies things if you are publishing services.

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by:sbumpas
ID: 34128547
Even with the TMG server is added to the domain, should it receive its' own dedicated DMZ?
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by:simonlimon
ID: 34128812
Looking at it, that TMG is a firewall it will probably be a gateway between various networks Client LAN, Server LAN and /or PErimeter network, maybe even Internet. How can it have a separate DMZ?

But I would definitely put it in a domain... Most namely you can use Kewrberos delegation, which for me is a great feature. Very user friendly but a bit more work for administrator. It works very good alongside a RADIUS one time password server or certificates with smartcards.
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by:sbumpas
ID: 34129162
I'm planning on using TMG specifically as an edge device, with no user authentication required for Internet access.  60% of our users are on public wireless/kiosks, and are not part of our domain.  

In this scenario, what would be the benefit of kereberos delegation (I'm unfamiliar with that concept)?
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by:simonlimon
ID: 34129184
KErberos delegation is used for Delegating credentials, and is solely used in web publishing. If you don't publish any resources to the Internet with the TMG you won't need this. Also, I would suggest you read this article about domain memberships.

http://www.isaserver.org/tutorials/Debunking-Myth-that-ISA-Firewall-Should-Not-Domain-Member.html

But if you ask me, I would have TMG / ISA as a domain member...
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by:Keith Alabaster
ID: 34130044
There is no benefit in Kerberos delegation based on your stated activities.
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by:sbumpas
ID: 34131254
By adding the server to the domain, will that enable per user logging for domain crdentials?  I can't find any reference to that in the administrator's guide.
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by:Keith Alabaster
Keith Alabaster earned 75 total points
ID: 34131336
It makes life easier - access rules will need to be able to request and validate user credentials by setting per-rule requirements and if the server is part of the domain this simplifies matters as you can imagine.
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by:Mohamed Khairy
ID: 34131675
You can use domain groups and users on the rules and you don’t need to create to use Radius or LDAP servers to validate users credentials which in case of radius or LDAP increase the risk of account lockout.

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by:sbumpas
ID: 34135737
One last question - I'm still a little unclear on the network design for a TMG server.  Currently, i have a VLAN dedicated to the connection between my firewall and my switch stack (think of it as a /30 network).  Would the same apply to a TMG server that's part of my LAN domain?  Seems like it would, as DNS could be set manually which would allow for domain membership without any hassle.
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by:simonlimon
simonlimon earned 75 total points
ID: 34270385
In this scenario the tmg server would use an ip inside this network that belongs to that /30 network.

You would then proxy your clients to this as a proxy.

Or you could put the tmg in your lan, give it an ip there and proxy from your lan to the internet.

Third option would be to five tmg an ip on that 30 network and an ip on your lan. And it would be a gateway between these two networks.

But the decision is upto you.

If i were you i would have it as a gateway between the lan and /30 network. It allows greater control for the outside as you control outgoing traffic on one point
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