Cisco Network Admission Control (NAC) is a system to enforce the security policy of your company on all devices attempting network access. The Cisco NAC solution is made up of many different pieces of hardware, software, and services; this article will explain its many pieces.

What hardware makes up Cisco’s NAC solution?

On Cisco’s network security solutions Web page, you’ll find the following list of Cisco technologies, all of which play a part in the complete Cisco NAC solution:

Let’s discuss some of the more critical pieces of Cisco’s NAC solution.

Cisco NAC-enabled routers

The recently released Cisco router NAT module enforces NAC at the remote branch locations or ancillary buildings of a campus. Apart from that, the NAC router module also improves the overall security of the network by making sure that all incoming users and devices comply with security policies.

Additionally, the Cisco NAC router module (part # NME-NAC-K9) brings the capabilities of Cisco NAC Appliance Server to Cisco 2800 and 3800 Series Integrated Services Routers. This module helps network administrators by not having to deploy NAC appliances across the board and it helps to consolidate the administrative tasks into fewer boxes.

Amazingly, this module is actually a 1 GHz Intel Celeron PC, with 512 MB RAM, 64 MB of Compact Flash, and an 80 GB SATA hard drive. All that fits onto a single 1-pound module that slides into a router and enforces your security policies. This module requires a 2800 or 3800 series router running IOS 12.4(11)T or later.

Cisco NAC Appliance

The single most popular piece of the Cisco NAC solution has been the Cisco NAC Appliance. As evident from the name itself, Cisco NAC Appliance is an appliance-based solution that offers fast deployment, policy management, and enforcement of security policies.

With the Cisco NAC Appliance, you can opt for an in-band or out-of-band solution. The in-band solution is for smaller deployments. As your network grows into a more campus environment, you may not be able to keep the in-band design. In that case, you can move to the out-of-band deployment scenario.

Here are some advantages of the Cisco NAC Appliance:

  • Identity: At the point of authentication, the Cisco NAC Appliance recognizes users, as well as their devices and their responsibility in the network.
  • Compliance: Cisco NAC Appliance also takes into account whether machines are compliant with security policies or not. This includes enforcing operating system updates, antivirus definitions, firewall settings, and antispyware software definitions.
  • Quarantine: If the machines attempting to gain access don’t meet the policies of the network, the Cisco NAC Appliance can quarantine these machines and bring them into compliance (by applying patches or changing settings), before releasing them onto the network.

For more information about the Cisco NAC Appliance, see the Cisco NAC Appliance datasheet.

Cisco Secure Access Control Server (ACS)

The Cisco ACS Server could be called the “brain” of the Cisco NAC solution. It is here that users’ credentials are checked to see if they are valid, policies are sent back to be enforced, and activities are logged. The ACS server is called an AAA Server because it performs authentication, authorization, and accounting.

This server runs on an existing Windows server in your organization and can use other existing databases in your organization to verify users’ credentials. For example, most companies have ACS point toward their Windows Active Directory (AD) system to look up credentials. If those credentials are valid, then ACS can enforce network authorization polices on those users, with the help of the network hardware: NAC Appliance, Router NAC module, or ASA/PIX firewalls.

Cisco Security Agent (CSA)

Cisco CSA is a software client that is run on every machine in an organization. These clients talk to a centralized policy server. Together, these software applications know what software and activities occurring on each PC in the organization are or are not “normal.” The CSA agent may alert on or block certain activities that it sees as abnormal.

When compared to anti-virus software that depends on definition updates to stay current, Cisco touts that the CSA never needs updating because it is constantly “learning” and monitoring activities, not definitions of viruses.

For more information about the Cisco CSA solution, see the Cisco CSA datasheet.

Cisco Trust Agent (CTA)

You can think of the Cisco Trust Agent as the “NAC Client.” The CTA runs on each PC in the organization. It talks to the NAC Appliance, for example, to tell it about the state of the device attempting to access the network. For example, the CTA reports the version of the OS, patch level, the AV definition level, the firewall status, and more. According to Cisco, the CTA “interrogates devices.” You can obtain CTA free of charge from Cisco Systems.

CiscoWorks Security Information Management Solution (CW-SIMS)

The CiscoWorks Security Information Management Solution (CW-SIMS) is the centralized repository that all Cisco devices use for security logging and other information. According to Cisco, this application “integrates, correlates, and analyzes security event data from the enterprise network to improve visibility and provide actionable intelligence for strengthening an organization’s security.”

With so many security devices in your network, one application has to try to correlate all the logs and security information that is generated. According to Cisco, here are the features that the CW-SIMS offers:

  • Comprehensive Correlation: Statistical, rules-based, and vulnerability correlation of events as they happen, in real time, across all integrated Cisco network devices.
  • Threat Visualization: See a visual status and generate reports of all the security events as they happen across your network.
  • Incident Resolution Management: SIMs integrates with common helpdesk packages to track security events until resolution.
  • Integrated Knowledge Base: SIMS can be a source of knowledge about security issues and how they are resolved.
  • Real-Time Notification: SIMS can notify security admins, in real time, when events occur.

For more information about the Cisco CW-SIMS solution, see the Cisco SW-SIMS datasheet.

Cisco Security Monitoring, Analysis, and Response System (MARS)

While MARS may seem similar to CW-SIMS, it is quite different. MARS actually understands the configuration and topology of your network. You can think of MARS as a “virtual security admin” for your network — working while you sleep.

MARS uses NetFlow data from Cisco routers to have a real-time understanding of network traffic. It knows what is considered normal and what is not; this is called behavioral analysis. With behavioral analysis, MARS can stop abnormal network traffic. MARS has over 150 audit compliance templates and will make recommendations on how to remediate threats to your network.

MARS is actually an appliance that you install on your network. This appliance comes in a variety of sizes and license levels based on the size of your network.

In summary

To be a complete solution that can fulfill the Cisco Self-Defending Network framework, the hardware and software of Cisco’s NAC solution must integrate well. With nine or more different pieces of hardware and software related to NAC, the challenge of acquiring (i.e., affording), learning to configure, deploying, and monitoring these solutions can be a large task for any organization. While having the centralized software applications like CW-SIMS and MARS can really bring it all together, those applications will take time, effort, and expertise to master. For this reason, I can relate to anyone who says that deploying a security solution is difficult.