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Cisco ASA Firewall settings

Posted on 2011-09-27
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Last Modified: 2012-05-12
My environment has two separate domains, with a Cisco ASA 5520 acting as Firewall/router in between the 2 domains, and between them and the internet.

Domain A uses the "Inside" interface and has 3 domain controllers
DCA1  192.168.1.1
DCA2  192.168.1.2
DCA3  192.168.1.3

Domain B uses the "Public" interface and has 2 domain controllers
DCB1  192.168.2.1
DCB2  192.168.2.2

I need to set up domain trust between the domain controllers in the 2 domains.

Right now, All domain controllers on domain A can ping all DC's on domain B.
NO domain controllers on domain B can ping any DC's on domain A.

What access rules do I need to configure on the ASA to allow DCB1 and DCB2 access to DCA1, DCA2 & DCA3, while blocking any other traffic from domain B to domain A?

I would appreciate some assistance, as right now all traffic from B to A is blocked and I cannot create the trust.
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Question by:Andrea_
7 Comments
 
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by:MikeKane
MikeKane earned 150 total points
ID: 36711668
Not an optimal setup from a networking standpoint.    The ASA uses 2 zones like this for security where inside is trusted and outside is not trusted.     In order to get device on the outside to speak with devices on the inside, you need to create a Static NAT from outside to inside, create an access-list to allow the traffic, and finally apply that ACL to an interface.  

Something like this:


static (inside, outside) 192.168.1.1 192.168.1.1 netmask 255.255.255.255
static (inside, outside) 192.168.1.2 192.168.1.2 netmask 255.255.255.255
static (inside, outside) 192.168.1.3 192.168.1.3 netmask 255.255.255.255

access-list outside_in extended permit ip 192.168.2.0 255.255.255.0 host 192.168.1.1
access-list outside_in extended permit ip 192.168.2.0 255.255.255.0 host 192.168.1.2
access-list outside_in extended permit ip 192.168.2.0 255.255.255.0 host 192.168.1.3

access-group outside_in in interface outside

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Author Comment

by:Andrea_
ID: 36711760
Sorry, I left out some key information.  
Both of those interfaces are on the inside.
The ASA actually has 5 interfaces configured (1 outside, 4 inside):
*** Outside  (198.111.167.xxx)
Inside  (192.168.255.1)
Public  (192.168.2.1)
Publicwlan (192.168.4.1)
Management (192.168.1.1)

Am I correct that the rules would be different since these interfaces are both internal?
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Author Comment

by:Andrea_
ID: 36713736
Can anyone help me?  I really need to get these domain controllers talking to each other!
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LVL 79

Accepted Solution

by:
lrmoore earned 200 total points
ID: 36713950
What are the security levels of the 2 interfaces?
1st, make them the same
2nd, check the box to allow same-security traffic inter-interface
3rd, create a network static
static (Inside,Public) 192.168.255.0 192.168.255.0 netmask 255.255.255.0
4th, create an access-list
access-list Public-Inside permit ip 192.168.2.0 255.255.255.0 192.168.255.0 255.255.255.0
5th, apply the acl to the Public interface
access-group Public-Inside in interface Public
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Author Comment

by:Andrea_
ID: 36714001
I want to make sure I understand your directions.  
Step 3, is that creating a static NAT?  or is there another type of static network I should be configuring?
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LVL 18

Assisted Solution

by:fgasimzade
fgasimzade earned 150 total points
ID: 36715781
Well, if security level is the same you would not need static NAT. Just make security levels the same and issue same-security traffic inter-interface - this will allow communication from one LAN to another.
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LVL 1

Author Comment

by:Andrea_
ID: 36717663
Thanks to all of you for your help.  
My solution ended up being this:
In the ASDM console:
Configuration- Firewall- Public Servers-
inside 192.168.1.1 ip public 192.168.1.1
inside 192.168.1.2 ip public 192.168.1.2
inside 192.168.1.3 ip public 192.168.1.3

That allowed my domain B servers to find my domain A servers, so that my access rules would work.
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