Network Policy Server and Cisco RADIUS Authentication

Setting up RADIUS authentication between Cisco devices and Network Policy Server (NPS) in Windows Server 2008 is a bit different than in previous versions of Windows.

Here is a technet page with lots of good info on NPS:

For now, I am just going to list the instructions needed to get up and going with NPS to allow your server to act as an authentication point for your Cisco switches/routers. This may work with other devices that can use radius authentication, but I have not tested it. YMMV.

1. Install the Network Policy Server service. It is a component under ‘Network Policy and Access Services’.

2. Open the Network Policy Server console from Administrative Tools.

3. Create a new radius client for the Cisco device. The process for this is very similar to the process in Server 2000/2003. You just need the device IP, choose the “radius standard” type, and make up a shared secret.

4. “Register server in Active Directory” by right-clicking on the “NPS (local)” item in the console. This will allow NPS to query AD when an authentication request comes in.

5.  Next, create a “Connection Request Policy”.  This is the step that is new to the process, and was not required before Server 2008.  Before, this was integrated into the remote access policy, as it was previously called.  The connection request policy doesn’t need to be anything complex.  The first step is to set the network access server type to “Unspecified”.

Next, add at least one condition to the policy.  I usually use the “day and time restrictions”, and then set it to ‘permitted’ 24×7.  Obviously, the condition(s) you choose should conform to your company’s security policy, so you may need something different here.

Finally, On the Settings tab, under Authentication, choose the radio button for “Authenticate requests on this server”.

6.  Create a Network Policy, formerly known as a remote access policy in previous versions of Windows Server.  On the Overview tab, configure the policy to use the network access server type of “Unspecified”.  In addition, set the access permission setting to “Grant Access”.

On the Conditions tab, add at least one condition.  Typically, this will be the Windows Group that is allowed to log in to the network devices.  As I said before, you may need to use different conditions than I show here due to your company security policy.

On the Constraints tab, the only change you should need to make is to enable the authentication method of “Unencrypted authentication (PAP, SPAP)”

Lastly, on the Settings tab, under Encryption, make sure that the “No Encryption” option is enabled.

7.  Point your network device(s) at this server for authentication.  The method for doing this varies depending on the make and model of your device.  With recent IOS images on Cisco switches, the commands will look something like this.

aaa new-model

aaa session-id common

aaa authentication login default group radius local

radius-server host auth-port 1812 acct-port 1813 key putyoursecretkeyhere

8.  Finally, test it!

Cisco PIX/ASA Causes SMTP Banner Corruption

Traffic inspection rules on a Cisco PIX or ASA firewall will sometimes cause the SMTP banner to appear corrupted.

When testing access to your mail server from outside, you may notice that the SMTP banner looks like this:

This is just a symptom of the problem, which is that the SMTP traffic inspection rule is interfering with the SMTP data stream.  Another symptom would be to see email messages destined for this server seemingly stuck in the SMTP queue on a server outside the network.  This can ultimately cause delayed and undeliverable mail, especially for larger messages, such as those with attachments.

The resolution for this problem is to disable the traffic inspection rule for SMTP/ESMTP on the Cisco PIX or ASA firewall.

On a PIX, this can be done from the command-line using the “no fixup protocol SMTP 25” command.  It can also be disabled from the PIX Device Manager (PDM).

On an ASA, it’s a little different.  From the command line (assuming your policy map is named “global_policy” and your class is named “inspection_default”):

CiscoASA(config)#policy-map global_policy
CiscoASA(config-pmap)#class inspection_default
CiscoASA(config-pmap-c)#no inspect esmtp 

From the Adaptive Security Device Manager (ASDM):

1.       Go to Security Policy –> Open the inspection rule:

2.       Go to the Rule Actions tab and uncheck the box next to ‘ESMTP’

3.       Test from outside the PIX/ASA again by telnetting to port 25; your SMTP banner should now look like this (I have masked the name of the server for privacy).

That’s it.  I have made it standard practice to just disable this inspection rule on all Cisco ASA firewalls that I deploy to avoid problems.

Posted via email from Aaron Johnstone

Set up VPN Client Access on a Cisco ASA

This article walks through how to configure a remote access VPN connection on a Cisco ASA 5500-series firewall.

1.  Log in to the Cisco ASDM
2.  Go to the Wizards menu and run the VPN Wizard.
3.  Choose the ‘Remote Access’ type on the VPN Tunnel Type page:

4.  Choose “Cisco VPN Client” for the VPN client type.
5.  Set your pre-shared key and your Tunnel Group Name
6.  Choose the client authentication method, either using the local user database or an AAA server group
7.  Add a DHCP pool to be used for users connecting using a VPN client; use a different subnet than one already in use on your LAN

8.   Configure the DHCP scope options, such as DNS, WINS, and default domain name
9.   Set the IKE and IPSec policies; I normally use the defaults, which currently are 3DES-SHA
10. Set the Address Translation Exemption and split tunneling options.  Typically, I use the internal network that the VPN-connected client will need access to and enable split tunneling.
11. Click Next, then Finish.
12. Go check the NAT exemption rules.  You should have a rule on the inside interface, exempting any traffic that is going to the VPN subnet (in this case from NAT.  Should look like this:

13. That is it; you are done!  You should be able to set up your Cisco VPN client, connect to the network, and test by pinging one of the servers on the internal LAN subnet.

    Posted via email from Aaron Johnstone

    Configure Cisco ASA remote access VPN to use RADIUS

    This article will help with setting up a Cisco ASA 5500-series firewall to use RADIUS to query a Microsoft Windows Active Directory domain controller to authenticate users who are connecting in using the Cisco VPN client.

    1. Install the Internet Authentication Service (IAS) Windows component

    2. Open the IAS console

    3. Add the Cisco ASA as a RADIUS client

    4. Edit the remote access policy in the IAS console as needed; enable “Unencrypted authentication (PAP, SPAP)” on the Authentication tab of the profile

    5. Connect to your ASA (assuming you are using the ASDM)

    6. Go to the Properties tab, then to AAA Setup à AAA Server Groups

    7. Create new server group

    8. Add a server to the group

    9. Test the authentication

    10. Go into your VPN settings on the ASA (General à Tunnel Group à properties of the remote access VPN)

    11. Go to the General à Authentication tab and change the Authentication Server Group property to the new AAA Server Group that you just created

    12. Check the box to enable LOCAL authentication if the server group fails

    13. Test it with an Active Directory user account from outside using the Cisco VPN client