Deploying NAC: Challenges and alternatives

What are some of the challenges in deploying NAC? What are the alternatives for LAN security?

You're not alone in asking these questions - we see customers all the time who know they need to control guests and contractors on their LAN but don't know where to start. Most find they can keep the initial NAC roll-out simple, deliver on their primary goals, and then follow a simple plan for expanding the scope of their deployment's functionality. Mercy Medical Center, for example, is following exactly this course - starting with providing guests Internet-only access and letting employees go anywhere on the LAN.

In your NAC deployment, you're likely to encounter three main challenges - the impact it has on your network, the difficulty of establishing policies, and the scope of your initial deployment. The good news is you can do a lot to reduce these challenges and gain a lot from your NAC deployment.

To understand NAC's impact on your network, you need to look at the degree to which it mandates changes, if any, to your endpoints, switches, VLANs or ACLs, and identity stores. The more you can reduce this impact, while still gaining significant control over what users can do on the LAN, the greater the return on investment from a "time to deploy" perspective.

For example, some NAC devices require cooperation from switches to enforce policy, so typically the switches need at least a software update. These solutions often provide only rudimentary post-admission control, relying on dropping users into a VLAN to limit their reach on the LAN. So you'll need to change your VLANs to support role-based segmentation and update your ACLs to enforce the appropriate blocking between user groups.

The second major challenge concerns establishing the appropriate policies, which is not ultimately IT's responsibility. Instead, IT needs to work with the lines of business to translate their desired policies, such as IBM contractors should get access only to IBM blade servers, into constructs that the NAC equipment can use and enforce.

To ease this challenge, IT should look for NAC architectures that make it easy to deploy and test the policies, by putting devices in "monitor only" mode, for example, and watching how many policy violations occur. If the number of violations is really large, it's more likely that the policy is wrong than that lots of people are behaving wrongly.

The third major challenge is scope - both scope of the overall deployment and scope of granularity in policies. A pervasive deployment, with extensive user controls in place, can quickly seem daunting.

To mitigate this difficulty, start with your most severe pain point and grow the deployment over time. Perhaps you start with network locations hosting guests and contractors first, and you create simple policies encompassing those user groups. Guests can go to the Internet only, the team customizing the SAP deployment can access only the SAP servers, and your employees can go everywhere. The key, of course, is to select a solution that can grow with you over time, as the location and granularity of your deployment grows.

Whether you'll need alternatives to NAC depends on the problem you're trying to solve. To broaden security capabilities, look for a solution that defines NAC as more than just admission control. You need to ask yourself, "Do I care about controlling users once they authenticate to my network?" If your answer is yes, you'll also want post-admission capabilities - such as controlling what applications a user can run or which servers a user can reach. With a more full-fledged view of security, you'll have lots of choices for the granularity of your NAC implementation.

Also keep in mind that NAC is highly complementary with other initiatives. Enterprises adopting Identity and Access Management (IAM) are concerned about role-based access control. The closer you can link such a project to a NAC architecture, the stronger both deployments will be, since the NAC solution can provide the network-level controls defined in the IAM project.

NAC, when extended to include full identity-based control over all users on the LAN, can help you protect your critical resources, and you can take many steps to limit its challenges and extract the greatest value.

Barsi is president and CEO, ConSentry Networks.

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Tom Barsi

Network World
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