Catalyst 6500 Release 12.2SX Software Configuration Guide

Configuring Network Admission Control

This chapter describes how to configure Network Admission Control (NAC) in Cisco IOS Release 12.2SX.

Note For complete syntax and usage information for the commands used in this chapter, see these publications:

•Cisco IOS Master Command List, at this URL:

http://www.cisco.com/en/US/docs/ios/mcl/allreleasemcl/all_book.html

•The Cisco IOS Security Command Reference, Release 12.3 at this URL:

http://www.cisco.com/en/US/products/ps6017/prod_command_reference_list.html

Tip For additional information about Cisco Catalyst 6500 Series Switches (including configuration examples and troubleshooting information), see the documents listed on this page:

http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html

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This chapter contains these sections:

•Understanding NAC

•Configuring NAC

•Monitoring and Maintaining NAC

Understanding NAC

These sections describe NAC:

•NAC Overview

•NAC Device Roles

•AAA Down Policy

•NAC IP Validation

•NAC and Switchover

NAC Overview

NAC is part of the Cisco Self-Defending Network Initiative that helps you identify, prevent, and adapt to security threats in your network. Because of the increased threat and impact of worms and viruses to networked businesses, NAC allows you to check and validate the antivirus status of endpoints or clients before granting network access.

Release 12.2(18)SXF2 and later releases supports NAC Layer 2 IP validation. Release 12.2(33)SXH and rebuilds support NAC Layer 3 IP validation. Release 12.2(33)SXI and later releases do not support NAC Layer 3 IP validation.

NAC Layer 2 IP (also known as LAN Port IP) operates on Layer 2 ports on edge switches. NAC Layer 2 IP validation has different methods for validation initiation, message exchange, and policy enforcement from the NAC Layer 2 IEEE 802.1x. LAN Port IP does not require IEEE 802.1x support on the host PCs. For additional information about IEEE 802.1x, see Chapter 60 "Configuring IEEE 802.1X Port-Based Authentication."

NAC Layer 3 IP (also known as NAC Gateway IP) operates on Layer 3 interfaces on distribution layer switches. An advantage of NAC Layer 3 IP is that access layer switches do not require any changes to use the NAC feature.

Note The NAC feature applies access controls only to IPv4 traffic. NAC does not restrict Layer 2-bridged traffic.

NAC provides posture validation for routed traffic. Posture validation reduces the exposure of a virus to the network. This feature allows network access based on the antivirus credentials of the network device that is requesting network access. These credentials may be antivirus software, a virus definitions file, or a particular virus scan engine version. Based on the antivirus credentials of the host, the requesting device is allowed access to the network or is restricted from network access.

If the client host fails the credential validation, then partial access to the network can be allowed by using the remediation feature. The remediation process redirects HTTP traffic from the client host to a web page URL that provides access to the latest antivirus files. The URL used by the remediation process resolves to a remediation server address defined as a part of the network access policy. The remediation server is where the latest antivirus files are located. These antivirus files can be downloaded or upgraded from this location.

NAC Device Roles

The devices in the network have specific roles when you use NAC as shown in Figure 59-1.

Figure 59-1 Posture Validation Devices

The following devices that support NAC on the network perform these roles:

•Endpoint system or client—This is a device (host) on the network such as a PC, workstation, or server. The host, which is running the Cisco Trust Agent (CTA) software, requests access to the LAN and switch services and responds to requests from the switch. This endpoint system is a potential source of virus infections, and its antivirus status needs to be validated before the host is granted network access.

–For NAC Layer 2 IP, the device is connected to an access port through a direct connection, an IP phone, or a wireless access point.

–For NAC Layer 3 IP, the device is one or more Layer 3 hops away from the switch.

The CTA software is also referred to as the posture agent or the antivirus client.

•Switch—This is a network access device, which provides validation services and policy enforcement.

–Edge switch—This is the network access device that provides NAC Layer 2 IP validation services and policy enforcement at the network edge and controls the physical access to the network based on the access policy of the client.

–Distribution switch—This is the NAC gateway, which provides validation services and policy enforcement at the Layer 3 network edge and controls access to the Layer 3 network based on the access policy of the client.

The encapsulation information in the EAP messages can be based on the User Datagram Protocol (UDP). When using UDP, the switch uses EAP over UDP (EAPoUDP) frames, which are also referred to as EoU frames.

The switch relays Extensible Authentication Protocol (EAP) messages between the endpoints and the authentication server.

•Authentication server—This device performs the actual validation of the client. The authentication server validates the antivirus status of the client, determines the access policy, and notifies the switch whether the client is authorized to access the LAN and switch services. Because the switch acts as the proxy, the EAP message exchange between the switch and authentication server is transparent to the switch.

The switch supports the Cisco Secure Access Control Server (ACS) Version 4.0 or later with RADIUS, authentication, authorization, and accounting (AAA), and EAP extensions.

The authentication server is also referred to as the posture server.

AAA Down Policy

The AAA down policy is a method of allowing a host to remain connected to the network if the AAA server is not available. Typical deployments of NAC use Cisco Secure ACS to validate the client posture and to pass policies back to the Network Access Device (NAD). If the AAA server cannot be reached when the posture validation occurs, instead of rejecting the user (that is, not providing the access to the network), an administrator can configure a default AAA down policy that can be applied to the host.

This policy is advantageous for the following reasons:

•While AAA is unavailable, the host will still have connectivity to the network, although it may be restricted.

•When the AAA server is again available, a user can be revalidated, and the user's policies can be downloaded from the ACS.

Note When the AAA server is down, the AAA down policy is applied only if there is no existing policy associated with the host. Typically, during revalidation when the AAA server goes down, the policies being used for the host are retained.

When the AAA policy is applied, the session state is maintained as AAA DOWN.

NAC IP Validation

The following sections describe NAC IP validation:

•NAC Layer 2 IP Validation

•NAC Layer 3 IP Validation

•Posture Validation

•Cisco Secure ACS and AV Pairs

•Audit Servers

•ACLs

•NAC Timers

NAC Layer 2 IP Validation

You can use NAC Layer 2 IP on the access port of an edge switch to which an endpoint system or client is connected. The device (host or client) can be a PC, a workstation, or a server that is connected to the access port through a direct connection, an IP phone, or a wireless access point, as shown in Figure 59-2.

When NAC Layer 2 IP is enabled, EAPoUDP only works with IPv4 traffic. The switch checks the antivirus status of the endpoint devices or clients and enforces access control policies.

Figure 59-2 Network Using NAC Layer 2 IP

NAC Layer 2 IP supports the posture validation of multiple hosts on the same Layer 2 port, as shown in Figure 59-2.

When you enable NAC Layer 2 IP validation on a Layer 2 port to which hosts are connected, the switch can use DHCP snooping and Address Resolution Protocol (ARP) snooping to identify connected hosts. The switch initiates posture validation after receiving an ARP packet or creating a DHCP snooping binding entry. When you enable NAC Layer 2 IP validation, ARP snooping is the default method to detect connected hosts. If you want the switch to detect hosts when a DHCP snooping binding entry is created, you must enable DHCP snooping.

NAC Layer 3 IP Validation

The gateway IP feature supports two types of posture validation (PV) triggers:

•Intercept ACLs

•ARP-based triggers (SVI interfaces only)

Intercept ACLs are configured to intercept inbound traffic from the clients and initiate PV if the traffic matches the ACL.

If the IP admission rule configured on an interface does not have an associated intercept ACL, the gateway uses ARP or DHCP events to trigger posture validation on the interface.

When the gateway learns a new client in its ARP cache, it initiates PV with the client. Using the ARP-based triggers reduces ACL TCAM usage, but it is only valid for clients that are one Layer 3 hop away from the gateway. Therefore, you can configure only SVIs (and not router ports) to have IP admission rules without an intercept ACL.

Posture Validation

If only dynamic ARP inspection is enabled on the access VLAN assigned to a Layer 2 port, posture validation is initiated when ARP packets pass the dynamic ARP inspection validation checks. However, if DHCP snooping and dynamic ARP inspection are enabled, when you create a DHCP snooping binding entry, posture validation is initiated through DHCP.

When posture validation is initiated, the switch creates an entry in the session table to track the posture validation status of the host and follows this process to determine the NAC policy:

1. If the host is in the exception list, the switch applies the user-configured NAC policy to the host.

2. If EoU bypass is enabled, the switch sends a nonresponsive-host request to the Cisco Secure ACS and applies the access policy from the server to the host. The switch inserts a RADIUS AV pair to the request to specify that the request is for a nonresponsive host.

3. If EoU bypass is disabled, the switch sends an EAPoUDP hello packet to the host, requesting the host antivirus condition. If no response is received from the host after the specified number of attempts, the switch classifies the host as clientless, and the host is considered to be a nonresponsive host. The switch sends a nonresponsive-host request to the Cisco Secure ACS and applies the access policy from the server to the host.

Note If a DHCP snooping binding entry for a client is deleted, the switch removes the client entry in the session table, and the client is no longer authenticated.

Exception Lists

An exception list has local profile and policy configurations. Use the identity profile to statically authorize or validate devices based on the IP address, MAC address, or device type. An identity profile is associated with a local policy that specifies the access control attributes.

You can bypass posture validation of specific hosts by specifying those hosts in an exception list and applying a user-configured policy to the hosts. After the entry is added to the EAPoUDP session table, the switch compares the host information to the exception list. If the host is in the exception list, the switch applies the configured NAC policy to the host. The switch also updates the EAPoUDP session table with the validation status of the client as POSTURE ESTAB.

EoU Bypass

The switch can use the EoU bypass feature to speed up posture validation of hosts that are not using the CTA. If EoU bypass is enabled, the switch does not contact the host to request the antivirus condition. Instead, the switch sends a request to the Cisco Secure ACS that includes the IP address, MAC address, service type, and EAPoUDP session ID of the host. The Cisco Secure ACS makes the access control decision and sends the policy to the switch.

If EoU bypass is enabled and the host is nonresponsive, the switch sends a nonresponsive-host request to the Cisco Secure ACS and applies the access policy from the server to the host.

If EoU bypass is enabled and the host uses CTA, the switch also sends a nonresponsive-host request to the Cisco Secure ACS and applies the access policy from the server to the host.

EAPoUDP Sessions

If the EoU bypass is disabled, the switch sends an EAPoUDP packet to initiate posture validation. While posture validation occurs, the switch enforces the default access policy. After the switch sends an EAPoUDP message to the host and the host responds to the antivirus condition request, the switch forwards the EAPoUDP response to the Cisco Secure ACS. If no response is received from the host after the specified number of attempts, the switch classifies the host as nonresponsive. After the ACS validates the credentials, the authentication server returns an Access-Accept message with the posture token and the policy attributes to the switch. The switch updates the EAPoUDP session table and enforces the access limitations, which provides segmentation and quarantine of poorly postured clients, or by denying network access.

There are two types of policies that apply during posture validation:

•Host Policy—The host policy consists of an ACL that enforces the access limitations as determined by the outcome of posture validation.

•URL Redirect Policy—The URL redirect policy provides a method to redirect all HTTP or HTTPS traffic to a remediation server that allows a noncompliant host to perform the necessary upgrade actions to become compliant.

The operation of the URL-redirect deny ACEs (typically to bypass the redirection of the HTTP traffic destined to remediation servers) is that the traffic to these ACEs is forwarded in hardware without applying the default interface and the downloaded host policies.

If this traffic (that is, the traffic that matches the deny URL redirect ACEs) is required to be filtered, you need to define a VLAN ACL on the Layer 2 access VLAN.

The URL redirect policy consists of the following:

•A URL that points to the remediation server.

•An ACL on the switch that causes all HTTP or HTTPS packets from the host other than those destined to the remediation server address to be captured and redirected to the switch software for the necessary HTTP redirection.

The ACL name for the host policy, the redirect URL, and the URL redirect ACL are conveyed using RADIUS Attribute-Value objects.

Cisco Secure ACS and AV Pairs

When NAC IP validation is enabled, the Cisco Secure ACS provides NAC AAA services by using RADIUS. Cisco Secure ACS gets information about the antivirus status of the endpoint system and validates the antivirus condition of the endpoint.

You can set these Attribute-Value (AV) pairs on the Cisco Secure ACS by using the RADIUS cisco-av-pair vendor-specific attributes (VSAs):

•CiscoSecure-Defined-ACL—Specifies the names of the downloadable ACLs on the Cisco Secure ACS. The switch gets the ACL name through the CiscoSecure-Defined-ACL AV pair in this format:

#ACL#-IP-name-number

name is the ACL name and number is the version number, such as 3f783768.

The Auth-Proxy posture code checks if the access control entries (ACEs) of the specified downloadable ACL were previously downloaded. If they were not, the Auth-Proxy posture code sends an AAA request with the downloadable ACL name as the username so that the ACEs are downloaded. The downloadable ACL is then created as a named ACL on the switch. This ACL has ACEs with a source address of any and does not have an implicit deny statement at the end. When the downloadable ACL is applied to an interface after posture validation is complete, the source address is changed from any to the host source IP address. The ACEs are prepended to the downloadable ACL applied to the switch interface to which the endpoint device is connected. If traffic matches the CiscoSecure-Defined-ACL ACEs, the appropriate NAC actions are taken.

•url-redirect and url-redirect-acl—Specifies the local URL policy on the switch. The switches use these cisco-av-pair VSAs as follows:

–url-redirect = <HTTP or HTTPS URL>

–url-redirect-acl = ACL name or number

These AV pairs enable the switch to intercept an HTTP or HTTPS request from the endpoint device and forward the client web browser to the specified redirect address from which the latest antivirus files can be downloaded. The url-redirect AV pair on the Cisco Secure ACS contains the URL to which the web browser will be redirected. The url-redirect-acl AV pair contains the name or number of an ACL that specifies the HTTP or HTTPS traffic to be redirected. The ACL must be defined on the switch. Traffic that matches a permit entry in the redirect ACL will be redirected.

These AV pairs may be sent if the host's posture is not healthy.

Note You can redirect the URL for either HTTP or HTTPS traffic but not for both at the same time. This situation occurs because the Cisco IOS software HTTP server can either listen to the HTTP port or to the HTTPS port but cannot listen to both at the same time.

For more information about AV pairs that are supported by Cisco IOS software, see the ACS configuration and command reference documentation about the software releases running on the AAA clients.

Audit Servers

End devices that do not run Cisco Trust Agent (CTA) will not be able to provide credentials when challenged by Network Access Devices. These devices are described as agentless or nonresponsive. The NAC architecture has been extended to incorporate audit servers. An audit server is a third-party server that can probe, scan, and determine security compliance of a host without the need for presence of Cisco trust agent on the host. The result of the audit server examination can influence the access servers to make host-specific network access policy decisions instead of enforcing a common restrictive policy for all nonresponsive hosts. You can build more robust host audit and examination functionality by integrating any third-party audit operations into the NAC architecture.

Figure 59-3 shows how audit servers fit into the typical topology.

Figure 59-3 NAC Device Roles

The architecture assumes that the audit server can be reached so that the host can communicate with it. When a host (endpoint device) makes network access through the NAD configured for posture validation, the network access device eventually requests the AAA server (Cisco Secure ACS) for an access policy to be enforced for the host. The AAA server can be configured to trigger a scan of the host with an external audit server. The audit server scan occurs asynchronously and can take several seconds to complete. During the time of the audit server scan, the AAA server conveys a minimal restrictive security policy to NAD for enforcement along with a short poll timer (session-timeout). The NAD polls the AAA server at the specified timer interval until the result is available from the audit server. After the AAA server receives the audit result, it computes an access policy based on the audit result and is sent down to NAD for enforcement on its next request.

ACLs

If you configure NAC IP validation on an interface, you must also configure a default security ACL on the same interface. The default ACL is applied to IP traffic for hosts that have not completed posture validation.

If the default ACL is configured on the switch and the Cisco Secure ACS sends a host access policy to the switch, the switch applies the policy to traffic from the host connected to a Layer 2 port. If the policy applies to the traffic, the switch forwards the traffic. If the policy does not apply, the switch applies the default ACL. If there is no default ACL configured, the traffic is permitted.

If the Cisco Secure ACS sends the switch a downloadable ACL that specifies a redirect URL as a policy-map action, this ACL takes precedence over the default ACL already configured on the Layer 2 port. The redirect URL ACL policy also takes precedence over the policy already configured on the host. If the default port ACL is not configured on the switch, the switch can still apply the downloadable ACL from the Cisco Secure ACS.

NAC Timers

The switch supports these timers:

•Hold Timer

•Idle Timer

•Retransmission Timer

•Revalidation Timer

•Status-Query Timer

Hold Timer

The hold timer prevents a new EAPoUDP session from immediately starting after the previous attempt to validate the session fails. This timer is used only when the Cisco Secure ACS sends a Accept-Reject message to the switch.

The default value of the hold timer is 180 seconds (3 minutes).

An EAPoUDP session might not be validated because the posture validation of the host fails, a session timer expires, or the switch or Cisco Secure ACS receives invalid messages. If the switch or authentication server continuously receives invalid messages, a malicious user might be trying to cause a denial-of-service attack.

Idle Timer

The idle timer controls how long the switch waits for an ARP packet from the postured host or a refreshed entry in the IP device tracking table to verify that the host is still connected. The idle timer works with a list of known hosts to track hosts that have initiated posture validation and the IP device tracking table.

The idle timer is reset when the switch receives an ARP packet or when an entry in the IP device tracking table is refreshed. If the idle timer expires, the switch ends the EAPoUDP session on the host, and the host is no longer validated.

The default value of the idle timer is calculated as the probe interval times the number of probe retries. By default, the idle timer default is 90 seconds which is the probe interval of 30 seconds times the number of probe retries of 3.

The switch maintains a list of known hosts to track hosts that have initiated posture validation. When the switch receives an ARP packet, it resets the aging timers for the list and the idle timer. If the aging time of the list expires, the switch sends an ARP probe to verify that the host is present. If the host is present, it sends a response to the switch. The switch updates the entry in the list of known hosts. The switch then resets the aging timers for the list and the idle timer. If the switch receives no response, the switch ends the session with the Cisco Secure ACS, and the host is no longer validated.

The switch uses the IP device tracking table to detect and manage hosts connected to the switch. The switch also uses ARP or DHCP snooping to detect hosts. By default, the IP device tracking feature is disabled on a switch.

You must enable the IP device tracking feature to use NAC IP validation.

When IP device tracking is enabled, and a host is detected, the switch adds an entry to the IP device tracking table that includes this information:

•IP and MAC address of the host

•Interface on which the switch detected the host

•Host state that is set to ACTIVE when the host is detected

If NAC Layer 2 or Layer 3 IP validation is enabled on an interface, adding an entry to the IP device tracking table initiates posture validation.

For the IP device tracking table, you can configure the number of times that the switch sends ARP probes for an entry before removing an entry from the table and you can also configure the number of seconds that the switch waits before resending the ARP probe. If the switch uses the default settings of the IP device tracking table, the switch sends ARP probes every 30 seconds for all the entries. When the host responds to the probe, the host state is refreshed and remains active. The switch can send up to three additional ARP probes at 30-second intervals if the switch does not get a response. After the maximum number of ARP probes are sent, the switch removes the host entry from the table. The switch ends the EAPoUDP session for the host if a session was set up.

Using the IP device tracking ensures that hosts are detected in a timely manner, despite the limitations of using DHCP. If a link goes down, the IP device tracking entries associated with the interface are not removed, and the state of entries is changed to inactive. The switch does not limit the number of active entries in the IP device tracking table but limits the number of inactive entries. When the table reaches the table size limit, the switch removes the inactive entries. If the table does not have inactive entries, the number of entries in the IP device tracking table increases. When a host becomes inactive, the switch ends the host session.

The table size limit is 2048.

After an interface link is restored, the switch sends ARP probes for the entry associated with the interface. The switch ages out entries for hosts that do not respond to ARP probes. The switch changes the state of hosts that respond to an active host and initiates posture validation.

Retransmission Timer

The retransmission timer controls the amount of time that the switch waits for a response from the client before resending a request during posture validation. Setting the timer value too low might cause unnecessary transmissions, and setting the timer value too high might cause poor response times.

The default value of the retransmission timer is 3 seconds.

Revalidation Timer

The revalidation timer controls the amount of time that a NAC policy is applied to a client that used EAPoUDP messages during posture validation. The timer starts after the initial posture validation is complete. The timer resets when the host is revalidated. The default value of the revalidation timer is 36000 seconds (10 hours).

You can specify the revalidation timer value on the switch by using the eou timeout revalidation seconds global configuration command. You can also specify the revalidation timer value on an interface by using the eou timeout revalidation seconds interface configuration command.

Note The revalidation timer can be configured locally on the switch or it can be downloaded from the control server.

The revalidation timer operation is based on Session-Timeout RADIUS attribute (Attribute[27]) and the Termination-Action RADIUS attribute (Attribute[29]) in the Access-Accept message from the Cisco Secure ACS running AAA. If the switch gets the Session-Timeout value, this value overrides the revalidation timer value on the switch.

If the revalidation timer expires, the switch action depends on one of these values of the Termination-Action attribute:

•If the value of the Termination-Action RADIUS attribute is the default, the session ends.

•If the switch gets a value for the Termination-Action attribute other than the default, the EAPoUDP session and the current access policy remain in effect during posture revalidation.

•If the value of the Termination-Action attribute is RADIUS, the switch revalidates the client.

•If the packet from the server does not include the Termination-Action attribute, the EAPoUDP session ends.

Status-Query Timer

The status-query timer controls the amount of time the switch waits before verifying that the previously validated client is present and that its posture has not changed. Only clients that were authenticated with EAPoUDP messages use this timer, which starts after the client is initially validated. The default value of the status-query timer is 300 seconds (5 minutes).

The timer resets when the host is reauthenticated. When the timer expires, the switch checks the host posture validation by sending a Status-Query message to the host. If the host sends a message to the switch that the posture has changed, the switch revalidates the posture of the host.

NAC and Switchover

When RPR mode redundancy is configured, a switchover causes the loss of all information about currently postured hosts. All sessions will be revalidated. Users will be unvalidated and may see service disruption.

With Release 12.2(33)SXH and later releases, if you are using SSO mode redundancy, you can enter the ip admission ha command to enable host session table synchronization to the standby supervisor engine. When the high availability feature is enabled, established postured hosts do not need to be revalidated when a switchover occurs, because they will not see any disruption from the switchover. Posture sessions that were not yet established prior to the SSO will need to be revalidated after the switchover.

Configuring NAC

The following sections describe how to configure NAC:

•Default NAC Configuration

•NAC IP Guidelines, Limitations, and Restrictions

•Configuring NAC IP Validation

•Configuring EAPoUDP

•Configuring Identity Profiles and Policies

•Configuring NAC High Availability

•Configuring a NAC AAA Down Policy

Default NAC Configuration

By default, NAC IP validation is disabled.

NAC IP Guidelines, Limitations, and Restrictions

•The NAC feature applies access controls only to IPv4 traffic. NAC does not restrict Layer 2 bridged traffic.

•IPv6 traffic does not trigger posture validation and NAC IP does not apply access policies to IPv6 traffic.

•Default ACLs must permit EAPoUDP traffic for NAC IP to function.

•DHCP traffic must be permitted in the interface default ACL and the host policy for DHCP snooping to function.

•If you want to forward HTTP and HTTPS requests from an endpoint device to a specific URL, you must enable the HTTP server feature. The url-redirect-acl AV pair should be defined as the URL ACL name. This ACL should contain a deny tcp any remediation server address eq www command followed by the permit ACEs for the HTTP traffic that is being redirected.

NAC Layer 2 IP Guidelines, Limitations, and Restrictions

When configuring NAC Layer 2 IP validation, follow these guidelines, limitations, and restrictions:

•You must configure Layer 3 routes from the switch to the host for the Layer 2 IP to operate correctly.

•Layer 2 IP is not allowed if the parent VLAN of the port has VACL capture configured.

•LAN Port IP (LPIP) ARP traffic redirected to the CPU cannot be spanned using the SPAN feature.

•NAC Layer 2 IP validation is not supported on trunk ports, tunnel ports, EtherChannel members, or routed ports. The Catalyst 6500 series switches support Layer 2 IP on EtherChannels.

•When NAC Layer 2 IP validation is enabled, you must configure an ACL on the Layer 2 port to which hosts are connected.

•NAC Layer 2 IP is not supported if the Layer 2 port is part of a private VLAN.

•NAC Layer 2 IP ARP traffic redirected to the CPU cannot be spanned using the SPAN feature.

•A denial-of-service attack might occur if the switch receives many ARP packets with different source IP addresses. To avoid this problem, you must configure the IP admission MLS rate-limiting feature using the mls rate-limit layer2 ip-admission command.

•If DAI is also enabled on the parent VLAN of the Layer 2 port, the IP admission rate limiting for ARP packets directed to the CPU is ineffective. In this situation, ARP inspection rate limiting is functional. ARP inspection rate limiting is performed in software and IP admission rate limiting is performed in hardware.

•When NAC Layer 2 IP and NAC Layer 2 IEEE 802.1x are enabled on the same access port, IEEE 802.1x authentication takes precedence. The posture of the host to which the port is connected might already have been validated, and the switch would have applied the access limitations based on IEEE 802.1x.

•DHCP snooping must be enabled if the switch wants to use DHCP lease grants to identify connected hosts. DHCP packets are permitted in DHCP environments in both the default interface and the downloaded host policy.

•If you want the end stations to send DNS requests before posture validation occurs, you must configure the named downloadable ACL on the Layer 2 port with ACEs permitting DNS packets.

•If NAC Layer 2 IP validation is configured on a Layer 2 port that belongs to a voice VLAN, the switch does not validate the posture of the IP phone. Make sure that the IP phone is on the exception list.

•If NAC Layer 2 IP validation is enabled, the NAC Layer 2 IP configuration takes precedence over VLAN ACLs and router ACLs that are configured on ingress interfaces. For example, when a VLAN ACL and a router ACL are configured, the operation applies the policies serially in the order of the LPIP policy to VLAN ACL to router ACL. The next policy is applied only when the traffic passes through the previous policy check. Any policy in the serial order denying the traffic causes the traffic to be denied. The downloaded LPIP host policy always overrides the default interface policy.

•If dynamic ARP inspection is enabled on the ingress VLAN, the switch initiates posture validation only after the ARP packets are validated.

•The traffic sent to the URL-redirect deny ACEs is forwarded in hardware without applying the default interface and the downloaded host policies. If this traffic (that is, the traffic matching the deny URL-redirect ACEs) requires filtering, you should define a VLAN ACL on the Layer 2 access VLAN. This configuration allows you to bypass the redirection of the HTTP traffic destined for the remediation servers.

NAC Layer 3 IP Guidelines, Limitations, and Restrictions

When configuring NAC Layer 3 IP validation, follow these guidelines, limitations, and restrictions:

•Only Release 12.2(33)SXH and rebuilds support NAC Layer 3 IP validation. Release 12.2(33)SXI and later releases do not support NAC Layer 3 IP validation.

•NAC Gateway feature is supported on Supervisor Engine 720 and Supervisor Engine 32-8GE.

•For ARP-based trigger, the GWIP detects host presence using the ARP probing mechanism.

•When you enable NAC Gateway IP validation on an interface, you must also configure a default Cisco IOS ACL on the interface.

•The traffic sent to the URL-redirect deny ACEs is forwarded in hardware without applying the default interface and the downloaded host policies. If this traffic (that is, the traffic matching the deny URL-redirect ACEs) requires filtering, you should define a Cisco IOS ACL on the interface. This configuration allows you to bypass the redirection of the HTTP traffic destined for the remediation servers.

•If IEEE 802.1x authentication in single-host mode and NAC Layer 2 IP validation are configured on a Layer 2 port, and IEEE 802.1x authentication of the connected hosts fails, the switch does not initiate posture validation when it receives DHCP or ARP packets from the host.

If IEEE 802.1x authentication is configured on the port, the port cannot send or receive traffic other than EAPOL frames until the client is successfully authenticated.

Configuring NAC IP Validation

To configure NAC Layer 2 IP validation, beginning in privileged EXEC mode, perform this task:

When configuring NAC IP validation, note the following guidelines:

•To remove the IP NAC rule on the switch, use the no ip admission name rule_name eapoudp global configuration command. To remove the IP NAC rule that was applied to a specific interface, use the no ip admission admission_name interface configuration command.

•To remove the EAPoUDP authentication methods, use the no aaa authentication eou default global configuration command. To configure the auth-proxy posture code to not obtain security associations from the AAA server, use the no aaa authorization auth-proxy default global configuration command.

•To disable the IP device tracking table and return the parameters for the table to the default values, use the no device tracking and the no device tracking probe {count | interval} global configuration commands.

•To configure the switch to not send the Framed-IP-Address attribute, use the no radius-server attribute 8 include-in-access-req global configuration command.

•To disable the logging of EAPoUDP system events, use the no eou logging global configuration command.

•To clear all NAC client device entries on the switch or on the specified interface, use the clear eou privileged EXEC command. To clear entries in the IP device tracking table, use the clear ip device tracking privileged EXEC command.

•If IEEE 802.1x authentication in single-host mode and NAC Layer 2 IP validation are configured on a Layer 2 port and IEEE 802.1x authentication of the connected hosts fails, the switch does not initiate posture validation when it receives DHCP or ARP packets from the host.

If IEEE 802.1x authentication is configured on the port, the port cannot send or receive traffic other than EAPOL frames until the client is successfully authenticated.

This example shows how to configure NAC Layer 2 IP validation on a switch interface:

Router# configure terminal

Router(config)# ip admission name nac eapoudp

Router(config)# access-list 5 permit any any

Router(config)# interface gigabitethernet 2/0/1

Router(config-if)# ip access-group 5 in

Router(config-if)# ip admission nac 

Router(config-if)# exit

Router(config)# aaa new-model

Router(config)# aaa authentication eou default group radius

Router(config)# radius-server host admin key rad123

Router(config)# radius-server vsa send authentication

Router(config)# ip device tracking probe count 2

Router(config)# eou logging

Router(config)# end

Configuring EAPoUDP

To configure the EAPoUDP, beginning in privileged EXEC mode, perform this task:

To return to the global default EAPoUDP values, use the no forms of the eou global configuration commands. To disable the EAPoUDP associations, use the no forms of the eou interface configuration commands.

Configuring Identity Profiles and Policies

To configure the identity profile and policy beginning in privileged EXEC mode, perform this task:

To remove the identity policy from the switch, use the no identity-policy policy_name global configuration command. To remove the identity profile, use the no identity profile eapoudp global configuration command. To not authorize the specified IP device and remove the specified policy from the device, use the no device {authorize | not-authorize} {ip-address ip_address | mac-address mac_address | type cisco ip phone} [policy policy_name] interface configuration command.

This example shows how to configure the identity profile and policy:

Router# configure terminal

Router(config)# identity policy policy1

Router(config-identity-policy)# access-group group1

Router(config)# identity profile eapoudp

Router(config-identity-prof)# device authorize ip address 10.10.142.25 policy policy1

Router(config-identity-prof)# exit

Router(config)# end

Configuring NAC High Availability

To configure IP admission high availability, perform this task:

Note You cannot enable the IP admission high availability feature if there are active Webauth or Posture sessions.

To disable IP admission high availability from the switch, use the no ip admission ha configuration command.

This example shows how to configure IP admission high availability:

Router# configure terminal

Router(config)# ip admission ha

Router(config)# ip admission ha update 50

Router(config)# end

Router(config)# clear ip admission ha stats

Router(config-identity-prof)# show ip admission ha stats 

Configuring a NAC AAA Down Policy

To configure NAC AAA down policy, perform this task:

The following example illustrates how to apply a AAA down policy:

Router# config t

Enter configuration commands, one per line.  End with CNTL/Z.

Router(config)# ip admission name AAA_DOWN eapoudp event timeout aaa policy identity 
global_policy

Router(config)# aaa new-model

Router(config)# aaa authorization network default local

Router(config)# aaa authentication eou default group radius

Router(config)# identity policy global_policy

Router(config-identity-policy)# ac

Router(config-identity-policy)# access-group global_acl

Router(config)# ip access-list extended global_acl

Router(config-ext-nacl)# permit ip any any

Router(config-ext-nacl)# exit

Router(config)# radius-server host 40.0.0.4 test username administrator idle-time 1 key 
cisco

Router(config)# radius-server dead-criteria tries 3

Router(config)# radius-server vsa send authentication

Router(config)# radius-server attribute 8 include-in-access-req

Router(config)# int fastEthernet 2/13

Router(config-if)# ip admission AAA_DOWN

Router(config-if)# exit

Router# show ip admission configuration

Show running output

-------------------

aaa new-model

aaa authentication eou default group radius

aaa authorization network default local 

ip admission name AAA_DOWN eapoudp event timeout aaa policy identity global_policy

identity policy global_policy

 access-group global_acl

interface FastEthernet2/13

 switchport

 switchport access vlan 222

 switchport mode access

 no ip address

 ip access-group 115 in

 ip admission AAA_DOWN

!

ip access-list extended global_acl

 permit ip any any

radius-server dead-criteria tries 3

radius-server attribute 8 include-in-access-req

radius-server host 40.0.0.4 auth-port 1645 acct-port 1646 test username administrator 
idle-time 1 key cisco

radius-server vsa send authentication

Router# show ip admission configuration 

Authentication global cache time is 60 minutes

Authentication global absolute time is 0 minutes

Authentication global init state time is 2 minutes

Auth-proxy name AAA_DOWN

   eapoudp list not specified auth-cache-time 60 minutes

   Identity policy name global_policy for AAA fail policy

Monitoring and Maintaining NAC

You can perform the tasks in these sections to monitor and maintain NAC:

•Clearing Table Entries

•Displaying NAC Information

Clearing Table Entries

To clear client entries in the EAPoUDP session table, use the clear eou privileged EXEC command. After the entries are removed, they are created only after the switch receives an ARP packet from the host or after it creates a DHCP binding entry for the host.

To clear entries in the IP device tracking table on the switch, use the clear ip device tracking privileged EXEC command.

Displaying NAC Information

To display NAC information, perform one of the following tasks:

Tip For additional information about Cisco Catalyst 6500 Series Switches (including configuration examples and troubleshooting information), see the documents listed on this page:

http://www.cisco.com/en/US/products/hw/switches/ps708/tsd_products_support_series_home.html

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