Catalyst 3750 Switch Software Configuration Guide, 12.2(25)SEC

Configuring IEEE 802.1x Port-Based Authentication

This chapter describes how to configure IEEE 802.1x port-based authentication on the Catalyst 3750 switch. IEEE 802.1x prevents unauthorized devices (clients) from gaining access to the network. Unless otherwise noted, the term switch refers to a standalone switch and to a switch stack.

Note For complete syntax and usage information for the commands used in this chapter, see the "RADIUS Commands" section in the Cisco IOS Security Commmand Reference, Release 12.2 and the command reference for this release.

This chapter consists of these sections:

•Understanding IEEE 802.1x Port-Based Authentication

•Configuring IEEE 802.1x Authentication

•Displaying IEEE 802.1x Statistics and Status

Understanding IEEE 802.1x Port-Based Authentication

The IEEE 802.1x standard defines a client-server-based access control and authentication protocol that prevents unauthorized clients from connecting to a LAN through publicly accessible ports unless they are properly authenticated. The authentication server authenticates each client connected to a switch port before making available any services offered by the switch or the LAN.

Until the client is authenticated, IEEE 802.1x access control allows only Extensible Authentication Protocol over LAN (EAPOL), Cisco Discovery Protocol (CDP), and Spanning Tree Protocol (STP) traffic through the port to which the client is connected. After authentication is successful, normal traffic can pass through the port.

These sections describe IEEE 802.1x port-based authentication:

•Device Roles

•Authentication Initiation and Message Exchange

•Ports in Authorized and Unauthorized States

•IEEE 802.1x Accounting

•IEEE 802.1x Accounting Attribute-Value Pairs

•IEEE 802.1x Host Mode

•Using IEEE 802.1x with Port Security

•Using IEEE 802.1x with Voice VLAN Ports

•Using IEEE 802.1x with VLAN Assignment

•Using IEEE 802.1x with Guest VLAN

•Using IEEE 802.1x with Wake-on-LAN

•Using IEEE 802.1x with Per-User ACLs

•IEEE 802.1x and Switch Stacks

Device Roles

With IEEE 802.1x port-based authentication, the devices in the network have specific roles as shown in Figure 10-1.

Figure 10-1 IEEE 802.1x Device Roles

•Client—the device (workstation) that requests access to the LAN and switch services and responds to requests from the switch. The workstation must be running IEEE 802.1x-compliant client software such as that offered in the Microsoft Windows XP operating system. (The client is the supplicant in the IEEE 802.1x specification.)

Note To resolve Windows XP network connectivity and IEEE 802.1x authentication issues, read the Microsoft Knowledge Base article at this URL: http://support.microsoft.com/support/kb/articles/Q303/5/97.ASP

•Authentication server—performs the actual authentication of the client. The authentication server validates the identity of the client and notifies the switch whether or not the client is authorized to access the LAN and switch services. Because the switch acts as the proxy, the authentication service is transparent to the client. In this release, the RADIUS security system with Extensible Authentication Protocol (EAP) extensions is the only supported authentication server. It is available in Cisco Secure Access Control Server Version 3.0 or later. RADIUS operates in a client/server model in which secure authentication information is exchanged between the RADIUS server and one or more RADIUS clients.

•Switch (edge switch or wireless access point)—controls the physical access to the network based on the authentication status of the client. The switch acts as an intermediary (proxy) between the client and the authentication server, requesting identity information from the client, verifying that information with the authentication server, and relaying a response to the client. The switch includes the RADIUS client, which is responsible for encapsulating and decapsulating the EAP frames and interacting with the authentication server.

When the switch receives EAPOL frames and relays them to the authentication server, the Ethernet header is stripped and the remaining EAP frame is re-encapsulated in the RADIUS format. The EAP frames are not modified during encapsulation, and the authentication server must support EAP within the native frame format. When the switch receives frames from the authentication server, the server's frame header is removed, leaving the EAP frame, which is then encapsulated for Ethernet and sent to the client.

The devices that can act as intermediaries include the Catalyst 3750, Catalyst 3560, Catalyst 3550, Catalyst 2970, Catalyst 2955, Catalyst 2950, Catalyst 2940 switches, or a wireless access point. These devices must be running software that supports the RADIUS client and IEEE 802.1x.

Authentication Initiation and Message Exchange

The switch or the client can initiate authentication. If you enable authentication on a port by using the dot1x port-control auto interface configuration command, the switch initiates authentication when the link state changes from down to up or periodically as long as the port remains up and unauthenticated. The switch sends an EAP-request/identity frame to the client to request its identity. Upon receipt of the frame, the client responds with an EAP-response/identity frame.

However, if during bootup, the client does not receive an EAP-request/identity frame from the switch, the client can initiate authentication by sending an EAPOL-start frame, which prompts the switch to request the client's identity.

Note If IEEE 802.1x is not enabled or supported on the network access device, any EAPOL frames from the client are dropped. If the client does not receive an EAP-request/identity frame after three attempts to start authentication, the client sends frames as if the port is in the authorized state. A port in the authorized state effectively means that the client has been successfully authenticated. For more information, see the "Ports in Authorized and Unauthorized States" section.

When the client supplies its identity, the switch begins its role as the intermediary, passing EAP frames between the client and the authentication server until authentication succeeds or fails. If the authentication succeeds, the switch port becomes authorized. For more information, see the "Ports in Authorized and Unauthorized States" section.

The specific exchange of EAP frames depends on the authentication method being used. Figure 10-2 shows a message exchange initiated by the client using the One-Time-Password (OTP) authentication method with a RADIUS server.

Figure 10-2 Message Exchange

Ports in Authorized and Unauthorized States

Depending on the switch port state, the switch can grant a client access to the network. The port starts in the unauthorized state. While in this state, the port that is not configured as a voice VLAN port disallows all ingress and egress traffic except for IEEE 802.1x, CDP, and STP packets. When a client is successfully authenticated, the port changes to the authorized state, allowing all traffic for the client to flow normally. If the port is configured as a voice VLAN port, the port allows VoIP traffic and IEEE 802.1x protocol packets before the client is successfully authenticated.

If a client that does not support IEEE 802.1x connects to an unauthorized IEEE 802.1x port, the switch requests the client's identity. In this situation, the client does not respond to the request, the port remains in the unauthorized state, and the client is not granted access to the network.

In contrast, when an IEEE 802.1x-enabled client connects to a port that is not running the IEEE 802.1x standard, the client initiates the authentication process by sending the EAPOL-start frame. When no response is received, the client sends the request for a fixed number of times. Because no response is received, the client begins sending frames as if the port is in the authorized state.

You control the port authorization state by using the dot1x port-control interface configuration command and these keywords:

•force-authorized—disables IEEE 802.1x authentication and causes the port to change to the authorized state without any authentication exchange required. The port sends and receives normal traffic without IEEE 802.1x-based authentication of the client. This is the default setting.

•force-unauthorized—causes the port to remain in the unauthorized state, ignoring all attempts by the client to authenticate. The switch cannot provide authentication services to the client through the port.

•auto—enables IEEE 802.1x authentication and causes the port to begin in the unauthorized state, allowing only EAPOL frames to be sent and received through the port. The authentication process begins when the link state of the port changes from down to up or when an EAPOL-start frame is received. The switch requests the identity of the client and begins relaying authentication messages between the client and the authentication server. Each client attempting to access the network is uniquely identified by the switch by using the client MAC address.

If the client is successfully authenticated (receives an Accept frame from the authentication server), the port state changes to authorized, and all frames from the authenticated client are allowed through the port. If the authentication fails, the port remains in the unauthorized state, but authentication can be retried. If the authentication server cannot be reached, the switch can resend the request. If no response is received from the server after the specified number of attempts, authentication fails, and network access is not granted.

When a client logs off, it sends an EAPOL-logoff message, causing the switch port to change to the unauthorized state.

If the link state of a port changes from up to down, or if an EAPOL-logoff frame is received, the port returns to the unauthorized state.

IEEE 802.1x Accounting

The IEEE 802.1x standard defines how users are authorized and authenticated for network access but does not keep track of network usage. IEEE 802.1x accounting is disabled by default. You can enable IEEE 802.1x accounting to monitor this activity on IEEE 802.1x-enabled ports:

•User successfully authenticates.

•User logs off.

•Link-down occurs.

•Re-authentication successfully occurs.

•Re-authentication fails.

The switch does not log IEEE 802.1x accounting information. Instead, it sends this information to the RADIUS server, which must be configured to log accounting messages.

IEEE 802.1x Accounting Attribute-Value Pairs

The information sent to the RADIUS server is represented in the form of Attribute-Value (AV) pairs. These AV pairs provide data for different applications. (For example, a billing application might require information that is in the Acct-Input-Octets or the Acct-Output-Octets attributes of a RADIUS packet.)

AV pairs are automatically sent by a switch that is configured for IEEE 802.1x accounting. Three types of RADIUS accounting packets are sent by a switch:

•START-sent when a new user session starts

•INTERIM-sent during an existing session for updates

•STOP-sent when a session terminates

Table 10-1 lists the AV pairs and when they are sent are sent by the switch:

You can view the AV pairs that are being sent by the switch by entering the debug radius accounting privileged EXEC command. For more information about this command, see the Cisco IOS Debug Command Reference, Release 12.2 at this URL:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios122/122sup/122debug

For more information about AV pairs, see RFC 3580, "IEEE 802.1X Remote Authentication Dial In User Service (RADIUS) Usage Guidelines."

IEEE 802.1x Host Mode

You can configure an IEEE 802.1x port for single-host or for multiple-hosts mode. In single-host mode (see Figure 10-1), only one client can be connected to the IEEE 802.1x-enabled switch port. The switch detects the client by sending an EAPOL frame when the port link state changes to the up state. If a client leaves or is replaced with another client, the switch changes the port link state to down, and the port returns to the unauthorized state.

In multiple-hosts mode, you can attach multiple hosts to a single IEEE 802.1x-enabled port. Figure 10-3 shows IEEE 802.1x port-based authentication in a wireless LAN. In this mode, only one of the attached clients must be authorized for all clients to be granted network access. If the port becomes unauthorized (re-authentication fails or an EAPOL-logoff message is received), the switch denies network access to all of the attached clients. In this topology, the wireless access point is responsible for authenticating the clients attached to it, and it also acts as a client to the switch.

With the multiple-hosts mode enabled, you can use IEEE 802.1x to authenticate the port and port security to manage network access for all MAC addresses, including that of the client.

Figure 10-3 Multiple Host Mode Example

Using IEEE 802.1x with Port Security

You can configure an IEEE 802.1x port with port security in either single-host or multiple-hosts mode. (You also must configure port security on the port by using the switchport port-security interface configuration command.) When you enable port security and IEEE 802.1x on a port, IEEE 802.1x authenticates the port, and port security manages network access for all MAC addresses, including that of the client. You can then limit the number or group of clients that can access the network through an IEEE 802.1x port.

These are some examples of the interaction between IEEE 802.1x and port security on the switch:

•When a client is authenticated, and the port security table is not full, the client MAC address is added to the port security list of secure hosts. The port then proceeds to come up normally.

When a client is authenticated and manually configured for port security, it is guaranteed an entry in the secure host table (unless port security static aging has been enabled).

A security violation occurs if the client is authenticated, but the port security table is full. This can happen if the maximum number of secure hosts has been statically configured or if the client ages out of the secure host table. If the client address is aged, its place in the secure host table can be taken by another host.

If the security violation is caused by the first authenticated host, the port becomes error-disabled and immediately shuts down.

The port security violation modes determine the action for security violations. For more information, see the "Security Violations" section on page 25-9.

•When you manually remove an IEEE 802.1x client address from the port security table by using the no switchport port-security mac-address mac-address interface configuration command, you should re-authenticate the IEEE 802.1x client by using the dot1x re-authenticate interface interface-id privileged EXEC command.

•When an IEEE 802.1x client logs off, the port changes to an unauthenticated state, and all dynamic entries in the secure host table are cleared, including the entry for the client. Normal authentication then takes place.

•If the port is administratively shut down, the port becomes unauthenticated, and all dynamic entries are removed from the secure host table.

•Port security and a voice VLAN can be configured simultaneously on an IEEE 802.1x port that is in either single-host or multiple-hosts mode. Port security applies to both the voice VLAN identifier (VVID) and the port VLAN identifier (PVID).

For more information about enabling port security on your switch, see the "Configuring Port Security" section on page 25-7.

Using IEEE 802.1x with Voice VLAN Ports

A voice VLAN port is a special access port associated with two VLAN identifiers:

•VVID to carry voice traffic to and from the IP phone. The VVID is used to configure the IP phone connected to the port.

•PVID to carry the data traffic to and from the workstation connected to the switch through the IP phone. The PVID is the native VLAN of the port.

Before Cisco IOS Release 12.1(14)EA1, a switch in single-host mode accepted traffic from a single host, and voice traffic was not allowed. In multiple-hosts mode, the switch did not accept voice traffic until the client was authenticated on the primary VLAN, thus making the IP phone inoperable until the user logged in.

With Cisco IOS Release 12.1(14)EA1 and later, the IP phone uses the VVID for its voice traffic, regardless of the authorization state of the port. This allows the phone to work independently of IEEE 802.1x authentication.

In single-host mode, only the IP phone is allowed on the voice VLAN. In multiple-hosts mode, additional clients can send traffic on the voice VLAN after a supplicant is authenticated on the PVID. When multiple-hosts mode is enabled, the supplicant authentication affects both the PVID and the VVID.

A voice VLAN port becomes active when there is a link, and the device MAC address appears after the first CDP message from the IP phone. Cisco IP phones do not relay CDP messages from other devices. As a result, if several IP phones are connected in series, the switch recognizes only the one directly connected to it. When IEEE 802.1x is enabled on a voice VLAN port, the switch drops packets from unrecognized IP phones more than one hop away.

When IEEE 802.1x is enabled on a port, you cannot configure a port VLAN that is equal to a voice VLAN.

Note If you enable IEEE 802.1x on an access port on which a voice VLAN is configured and to which a Cisco IP Phone is connected, the Cisco IP phone loses connectivity to the switch for up to 30 seconds.

For more information about voice VLANs, see Chapter 15, "Configuring Voice VLAN."

Using IEEE 802.1x with VLAN Assignment

Before Cisco IOS Release 12.1(14)EA1, when an IEEE 802.1x port was authenticated, it was authorized to be in the access VLAN configured on the port even if the RADIUS server returned an authorized VLAN from its database. Recall that an access VLAN is a VLAN assigned to an access port. All packets sent from or received on this port belong to this VLAN.

However, with Cisco IOS Release 12.1(14)EA1 and later releases, the switch supports IEEE 802.1x with VLAN assignment. After successful IEEE 802.1x authentication of a port, the RADIUS server sends the VLAN assignment to configure the switch port. The RADIUS server database maintains the username-to-VLAN mappings, assigning the VLAN based on the username of the client connected to the switch port. You can use this feature to limit network access for certain users.

When configured on the switch and the RADIUS server, IEEE 802.1x with VLAN assignment has these characteristics:

•If no VLAN is supplied by the RADIUS server or if IEEE 802.1x authorization is disabled, the port is configured in its access VLAN after successful authentication.

•If IEEE 802.1x authorization is enabled but the VLAN information from the RADIUS server is not valid, the port returns to the unauthorized state and remains in the configured access VLAN. This prevents ports from appearing unexpectedly in an inappropriate VLAN because of a configuration error.

Configuration errors could include specifying a VLAN for a routed port, a malformed VLAN ID, a nonexistent or internal (routed port) VLAN ID, or an attempted assignment to a voice VLAN ID.

•If IEEE 802.1x authorization is enabled and all information from the RADIUS server is valid, the port is placed in the specified VLAN after authentication.

•If the multiple-hosts mode is enabled on an IEEE 802.1x port, all hosts are placed in the same VLAN (specified by the RADIUS server) as the first authenticated host.

•If IEEE 802.1x and port security are enabled on a port, the port is placed in the RADIUS server-assigned VLAN.

•If IEEE 802.1x is disabled on the port, it is returned to the configured access VLAN.

When the port is in the force authorized, force unauthorized, unauthorized, or shutdown state, it is put into the configured access VLAN.

If an IEEE 802.1x port is authenticated and put in the RADIUS server-assigned VLAN, any change to the port access VLAN configuration does not take effect.

The IEEE 802.1x with VLAN assignment feature is not supported on trunk ports, dynamic ports, or with dynamic-access port assignment through a VLAN Membership Policy Server (VMPS).

To configure VLAN assignment you need to perform these tasks:

•Enable AAA authorization by using the network keyword to allow interface configuration from the RADIUS server.

•Enable IEEE 802.1x. (The VLAN assignment feature is automatically enabled when you configure IEEE 802.1x on an access port).

•Assign vendor-specific tunnel attributes in the RADIUS server. The RADIUS server must return these attributes to the switch:

–[64] Tunnel-Type = VLAN

–[65] Tunnel-Medium-Type = 802

–[81] Tunnel-Private-Group-ID = VLAN name or VLAN ID

Attribute [64] must contain the value VLAN (type 13). Attribute [65] must contain the value 802 (type 6). Attribute [81] specifies the VLAN name or VLAN ID assigned to the IEEE 802.1x-authenticated user.

For examples of tunnel attributes, see the "Configuring the Switch to Use Vendor-Specific RADIUS Attributes" section on page 9-29.

Using IEEE 802.1x with Guest VLAN

You can configure a guest VLAN for each IEEE 802.1x port on the switch to provide limited services to clients, such as downloading the IEEE 802.1x client. These clients might be upgrading their system for IEEE 802.1x authentication, and some hosts, such as Windows 98 systems, might not be IEEE 802.1x-capable.

When you enable a guest VLAN on an IEEE 802.1x port, the switch assigns clients to a guest VLAN when the authentication server does not receive a response to its EAPOL request/identity frame or when EAPOL packets are not sent by the client.

Before Cisco IOS Release 12.2(25)SE, the switch did not maintain the EAPOL packet history and allowed clients that failed authentication access to the guest VLAN, regardless of whether EAPOL packets had been detected on the interface. You can enable this optional behavior by using the dot1x guest-vlan supplicant global configuration command.

With Cisco IOS Release 12.2(25)SE and later, the switch maintains the EAPOL packet history. If another EAPOL packet is detected on the interface during the lifetime of the link, network access is denied. The EAPOL history is reset upon loss of the link.

Any number of IEEE 802.1x-incapable clients are allowed access when the switch port is moved to the guest VLAN. If an IEEE 802.1x-capable client joins the same port on which the guest VLAN is configured, the port is put into the unauthorized state in the user-configured access VLAN, and authentication is restarted.

Guest VLANs are supported on IEEE 802.1x ports in single-host or multiple-hosts mode.

You can configure any active VLAN except an RSPAN VLAN, private VLAN, or a voice VLAN as an IEEE 802.1x guest VLAN. The guest VLAN feature is not supported on internal VLANs (routed ports) or trunk ports; it is supported only on access ports.

For more information, see the "Configuring a Guest VLAN" section.

Using IEEE 802.1x with Wake-on-LAN

The IEEE 802.1x wake-on-LAN (WoL) feature allows dormant PCs to be powered when the switch receives a specific Ethernet frame, known as the magic packet. You can use this feature in environments where administrators need to connect to systems that have been powered down.

When hosts that use WoL are attached through IEEE 802.1x ports and the host powers down, the IEEE 802.1x port becomes unauthorized. In this state, the port can only receive and send EAPOL packets, and WoL magic packets cannot reach the host. When the PC is powered down, it is not authenticated, and the switch port is not opened.

When the switch uses IEEE 802.1x with WoL, the switch sends packets to unauthorized IEEE 802.1x ports. This feature is also known as the Unidirectional Controlled Port in the IEEE 802.1x specification.

Note If PortFast is not enabled on the port, the port is forced to the bidirectional state.

Unidirectional State

When you configure a port as unidirectional by using the dot1x control-direction in interface configuration command, the port changes to the spanning-tree forwarding state.

When WoL is enabled, the connected host is in the sleeping mode or power-down state. The host does not exchange traffic with other devices in the network. If the host connected to the unidirectional port that cannot send traffic to the network, the host can only receive traffic from other devices in the network. If the unidirectional port receives incoming traffic, the port returns to the default bidirectional state, and the port changes to the spanning-tree blocking state. When the port changes to the initialize state, no traffic other than EAPOL packet is allowed. When the port returns to the bidirectional state, the switch starts a 5 minute timer. If the port is not authenticated before the timer expires, the port becomes a unidirectional port.

Bidirectional State

When you configure a port as bidirectional by using the dot1x control-direction both interface configuration command, the port is access-controlled in both directions. In this state, the switch port does not receive or send packets.

Using IEEE 802.1x with Per-User ACLs

You can enable per-user access control lists (ACLs) to provide different levels of network access and service to an IEEE 802.1x-authenticated user. When the RADIUS server authenticates a user connected to an IEEE 802.1x port, it retrieves the ACL attributes based on the user identity and sends them to the switch. The switch applies the attributes to the IEEE 802.1x port for the duration of the user session. The switch removes the per-user ACL configuration when the session is over, if authentication fails, or if a link-down condition occurs. The switch does not save RADIUS-specified ACLs in the running configuration. When the port is unauthorized, the switch removes the ACL from the port.

You can configure router ACLs and input port ACLs on the same switch. However, a port ACL takes precedence over a router ACL. If you apply input port ACL to an interface that belongs to a VLAN, the port ACL takes precedence over an input router ACL applied to the VLAN interface. Incoming packets received on the port to which a port ACL is applied are filtered by the port ACL. Incoming routed packets received on other ports are filtered by the router ACL. Outgoing routed packets are filtered by the router ACL. To avoid configuration conflicts, you should carefully plan the user profiles stored on the RADIUS server.

RADIUS supports per-user attributes, including vendor-specific attributes. These vendor-specific attributes (VSAs) are in octet-string format and are passed to the switch during the authentication process. The VSAs used for per-user ACLs are inacl#<n> for the ingress direction and outacl#<n> for the egress direction. MAC ACLs are supported only in the ingress direction. The switch supports VSAs only in the ingress direction. It does not support port ACLs in the egress direction on Layer 2 ports. For more information, see "Configuring Network Security with ACLs."

Use only the extended ACL syntax style to define the per-user configuration stored on the RADIUS server. When the definitions are passed from the RADIUS server, they are created by using the extended naming convention. However, if you use the Filter-Id attribute, it can point to a standard ACL.

You can use the Filter-Id attribute to specify an inbound or outbound ACL that is already configured on the switch. The attribute contains the ACL number followed by .in for ingress filtering or .out for egress filtering. If the RADIUS server does not allow the .in or .out syntax, the access list is applied to the outbound ACL by default. Because of limited support of Cisco IOS access lists on the switch, the Filter-Id attribute is supported only for IP ACLs numbered 1 to 199 and 1300 to 2699 (IP standard and IP extended ACLs).

Only one IEEE 802.1x-authenticated user is supported on a port. If the multiple-hosts mode is enabled on the port, the per-user ACL attribute is disabled for the associated port.

The maximum size of the per-user ACL is 4000 ASCII characters.

For examples of vendor-specific attributes, see the "Configuring the Switch to Use Vendor-Specific RADIUS Attributes" section on page 9-29. For more information about configuring ACLs, see "Configuring Network Security with ACLs."

To configure per-user ACLs, you need to perform these tasks:

•Enable AAA authentication.

•Enable AAA authorization by using the network keyword to allow interface configuration from the RADIUS server.

•Enable IEEE 802.1x.

•Configure the user profile and VSAs on the RADIUS server.

•Configure the IEEE 802.1x port for single-host mode.

IEEE 802.1x and Switch Stacks

If a switch is added to or removed from a switch stack, IEEE 802.1x authentication is not affected as long as the IP connectivity between the RADIUS server and the stack remains intact. This statement also applies if the stack master is removed from the switch stack. Note that if the stack master fails, a stack member becomes the new stack master by using the election process described in Chapter 5, "Managing Switch Stacks," and the IEEE 802.1x authentication process continues as usual.

If IP connectivity to the RADIUS server is interrupted because the switch that was connected to the server is removed or fails, these events occur:

•Ports that are already authenticated and that do not have periodic re-authentication enabled remain in the authenticated state. Communication with the RADIUS server is not required.

•Ports that are already authenticated and that have periodic re-authentication enabled (with the dot1x re-authentication global configuration command) fail the authentication process when the re-authentication occurs. Ports return to the unauthenticated state during the re-authentication process. Communication with the RADIUS server is required.

For an ongoing authentication, the authentication fails immediately because there is no server connectivity.

If the switch that failed comes up and rejoins the switch stack, the authentications might or might not fail depending on the boot-up time and whether the connectivity to the RADIUS server is re-established by the time the authentication is attempted.

To avoid loss of connectivity to the RADIUS server, you should ensure that there is a redundant connection to it. For example, you can have a redundant connection to the stack master and another to a stack member, and if the stack master fails, the switch stack still has connectivity to the RADIUS server.

Configuring IEEE 802.1x Authentication

These sections contain this configuration information:

•Default IEEE 802.1x Configuration

•IEEE 802.1x Configuration Guidelines

•Upgrading from a Previous Software Release

•Configuring IEEE 802.1x Authentication (required)

•Configuring the Switch-to-RADIUS-Server Communication (required)

•Configuring Periodic Re-Authentication (optional)

•Manually Re-Authenticating a Client Connected to a Port (optional)

•Changing the Quiet Period (optional)

•Changing the Switch-to-Client Retransmission Time (optional)

•Setting the Switch-to-Client Frame-Retransmission Number (optional)

•Setting the Re-Authentication Number (optional)

•Configuring the Host Mode (optional)

•Configuring a Guest VLAN (optional)

•Resetting the IEEE 802.1x Configuration to the Default Values (optional)

•Configuring IEEE 802.1x Accounting (optional)

Default IEEE 802.1x Configuration

Table 10-2 shows the default IEEE 802.1x configuration.

IEEE 802.1x Configuration Guidelines

These are the IEEE 802.1x authentication configuration guidelines:

•When IEEE 802.1x is enabled, ports are authenticated before any other Layer 2 or Layer 3 features are enabled.

•The IEEE 802.1x protocol is supported on Layer 2 static-access ports, voice VLAN ports, and Layer 3 routed ports, but it is not supported on these port types:

–Trunk port—If you try to enable IEEE 802.1x on a trunk port, an error message appears, and IEEE 802.1x is not enabled. If you try to change the mode of an IEEE 802.1x-enabled port to trunk, an error message appears, and the port mode is not changed.

–Dynamic ports—A port in dynamic mode can negotiate with its neighbor to become a trunk port. If you try to enable IEEE 802.1x on a dynamic port, an error message appears, and IEEE 802.1x is not enabled. If you try to change the mode of an IEEE 802.1x-enabled port to dynamic, IEEE 802.an error message appears, and the port mode is not changed.

–Dynamic-access ports—If you try to enable IEEE 802.1x on a dynamic-access (VLAN Query Protocol [VQP]) port, an error message appears, and IEEE 802.1x is not enabled. If you try to change an IEEE 802.1x-enabled port to dynamic VLAN assignment, an error message appears, and the VLAN configuration is not changed.

–EtherChannel port—Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an IEEE 802.1x port. If you try to enable IEEE 802.1x on an EtherChannel port, an error message appears, and IEEE 802.1x is not enabled.

Note In software releases earlier than Cisco IOS Release 12.2(18)SE, if IEEE 802.1x is enabled on a not-yet active port of an EtherChannel, the port does not join the EtherChannel.

–Switched Port Analyzer (SPAN) and Remote SPAN (RSPAN) destination ports—You can enable IEEE 802.1x on a port that is a SPAN or RSPAN destination port. However, IEEE 802.1x is disabled until the port is removed as a SPAN or RSPAN destination port. You can enable IEEE 802.1x on a SPAN or RSPAN source port.

•You can configure any VLAN except an RSPAN VLAN, private VLAN, or a voice VLAN as an IEEE 802.1x guest VLAN. The guest VLAN feature is not supported on internal VLANs (routed ports) or trunk ports; it is supported only on access ports.

•When IEEE 802.1x is enabled on a port, you cannot configure a port VLAN that is equal to a voice VLAN.

•The IEEE 802.1x with VLAN assignment feature is not supported on private-VLAN ports, trunk ports, dynamic ports, or with dynamic-access port assignment through a VMPS.

•You can configure IEEE 802.1x on a private-VLAN port, but do not configure IEEE 802.1x with port security, voice VLAN, guest VLAN, or a per-user ACL on private-VLAN ports.

•Before globally enabling IEEE 802.1x on a switch by entering the dot1x system-auth-control global configuration command, remove the EtherChannel configuration from the interfaces on which IEEE 802.1x and EtherChannel are configured.

•If you are using a device running the Cisco Access Control Server (ACS) application for IEEE 802.1x authentication with EAP-Transparent LAN Services (TLS) and EAP-MD5 and your switch is running Cisco IOS Release 12.1(14)EA1, make sure that the device is running ACS Version 3.2.1 or later.

•After you configure a guest VLAN for an IEEE 802.1x port to which a DHCP client is connected, you might need to get a host IP address from a DHCP server. You can also change the settings for restarting the IEEE 802.1x authentication process on the switch before the DHCP process on the client times out and tries to get a host IP address from the DHCP server. Decrease the settings for the IEEE 802.1x authentication process (IEEE 802.1x quiet period and switch-to-client transmission time).

Upgrading from a Previous Software Release

In Cisco IOS Release 12.1(14)EA1, the implementation for IEEE 802.1x changed from the previous release. Some global configuration commands became interface configuration commands, and new commands were added.

If you have IEEE 802.1x configured on the switch and you upgrade to Cisco IOS Release 12.1(14)EA1 or later, the configuration file will not contain the new commands, and IEEE 802.1x will not operate. After the upgrade is complete, make sure to globally enable IEEE 802.1x by using the dot1x system-auth-control global configuration command. If IEEE 802.1x was running in multiple-hosts mode on a port in the previous release, make sure to reconfigure it by using the dot1x host-mode multi-host interface configuration command.

Configuring IEEE 802.1x Authentication

To configure IEEE 802.1x port-based authentication, you must enable authentication, authorization, and accounting (AAA) and specify the authentication method list. A method list describes the sequence and authentication method to be queried to authenticate a user.

To allow per-user ACLs or VLAN assignment, you must enable AAA authorization to configure the switch for all network-related service requests.

This is the IEEE 802.1x AAA process:

Step 1 A user connects to a port on the switch.

Step 2 Authentication is performed.

Step 3 VLAN assignment is enabled, as appropriate, based on the RADIUS server configuration.

Step 4 The switch sends a start message to an accounting server.

Step 5 Re-authentication is performed, as necessary.

Step 6 The switch sends an interim accounting update to the accounting server that is based on the result of re-authentication.

Step 7 The user disconnects from the port.

Step 8 The switch sends a stop message to the accounting server.

Beginning in privileged EXEC mode, follow these steps to configure IEEE 802.1x port-based authentication:

Configuring the Switch-to-RADIUS-Server Communication

RADIUS security servers are identified by their hostname or IP address, hostname and specific UDP port numbers, or IP address and specific UDP port numbers. The combination of the IP address and UDP port number creates a unique identifier, which enables RADIUS requests to be sent to multiple UDP ports on a server at the same IP address. If two different host entries on the same RADIUS server are configured for the same service—for example, authentication—the second host entry configured acts as the fail-over backup to the first one. The RADIUS host entries are tried in the order that they were configured.

Beginning in privileged EXEC mode, follow these steps to configure the RADIUS server parameters on the switch. This procedure is required.

To delete the specified RADIUS server, use the no radius-server host {hostname | ip-address} global configuration command.

This example shows how to specify the server with IP address 172.20.39.46 as the RADIUS server, to use port 1612 as the authorization port, and to set the encryption key to rad123, matching the key on the RADIUS server:

Switch(config)# radius-server host 172.l20.39.46 auth-port 1612 key rad123

You can globally configure the timeout, retransmission, and encryption key values for all RADIUS servers by using the radius-server host global configuration command. If you want to configure these options on a per-server basis, use the radius-server timeout, radius-server retransmit, and the radius-server key global configuration commands. For more information, see the "Configuring Settings for All RADIUS Servers" section on page 9-29.

You also need to configure some settings on the RADIUS server. These settings include the IP address of the switch and the key string to be shared by both the server and the switch. For more information, see the RADIUS server documentation.

Configuring IEEE 802.1x Authentication Using a RADIUS Server

In Cisco IOS Release 12.2(25)SEC, you can also configure IEEE 802.1x authentication with a RADIUS server.

Beginning in privileged EXEC mode, follow these steps to configure IEEE 802.1x authentication with a RADIUS server. The procedure is optional.

This example shows how to configure IEEE 802.1x using a RADIUS server:

Switch# configure terminal

Switch(config)# interface gigabitethernet2/0/1

Switch(config-if)# dot1x reauthentication

Switch(config-if)# dot1x timeout reauth-period server

Configuring Periodic Re-Authentication

You can enable periodic IEEE 802.1x client re-authentication and specify how often it occurs. If you do not specify a time period before enabling re-authentication, the number of seconds between re-authentication attempts is 3600.

Beginning in privileged EXEC mode, follow these steps to enable periodic re-authentication of the client and to configure the number of seconds between re-authentication attempts. This procedure is optional.

To disable periodic re-authentication, use the no dot1x reauthentication interface configuration command. To return to the default number of seconds between re-authentication attempts, use the no dot1x timeout reauth-period interface configuration command.

This example shows how to enable periodic re-authentication and set the number of seconds between re-authentication attempts to 4000:

Switch(config-if)# dot1x reauthentication

Switch(config-if)# dot1x timeout reauth-period 4000

Manually Re-Authenticating a Client Connected to a Port

You can manually re-authenticate the client connected to a specific port at any time by entering the dot1x re-authenticate interface interface-id privileged EXEC command. This step is optional. If you want to enable or disable periodic re-authentication, see the "Configuring Periodic Re-Authentication" section.

This example shows how to manually re-authenticate the client connected to a port:

Switch# dot1x re-authenticate interface gigabitethernet2/0/1

Changing the Quiet Period

When the switch cannot authenticate the client, the switch remains idle for a set period of time and then tries again. The dot1x timeout quiet-period interface configuration command controls the idle period. A failed authentication of the client might occur because the client provided an invalid password. You can provide a faster response time to the user by entering a smaller number than the default.

Beginning in privileged EXEC mode, follow these steps to change the quiet period. This procedure is optional.

To return to the default quiet time, use the no dot1x timeout quiet-period interface configuration command.

This example shows how to set the quiet time on the switch to 30 seconds:

Switch(config-if)# dot1x timeout quiet-period 30

Changing the Switch-to-Client Retransmission Time

The client responds to the EAP-request/identity frame from the switch with an EAP-response/identity frame. If the switch does not receive this response, it waits a set period of time (known as the retransmission time) and then resends the frame.

Note You should change the default value of this command only to adjust for unusual circumstances such as unreliable links or specific behavioral problems with certain clients and authentication servers.

Beginning in privileged EXEC mode, follow these steps to change the amount of time that the switch waits for client notification. This procedure is optional.

To return to the default retransmission time, use the no dot1x timeout tx-period interface configuration command.

This example shows how to set 60 as the number of seconds that the switch waits for a response to an EAP-request/identity frame from the client before resending the request:

Switch(config-if)# dot1x timeout tx-period 60

Setting the Switch-to-Client Frame-Retransmission Number

In addition to changing the switch-to-client retransmission time, you can change the number of times that the switch sends an EAP-request/identity frame (assuming no response is received) to the client before restarting the authentication process.

Note You should change the default value of this command only to adjust for unusual circumstances such as unreliable links or specific behavioral problems with certain clients and authentication servers.

Beginning in privileged EXEC mode, follow these steps to set the switch-to-client frame-retransmission number. This procedure is optional.

To return to the default retransmission number, use the no dot1x max-req interface configuration command.

This example shows how to set 5 as the number of times that the switch sends an EAP-request/identity request before restarting the authentication process:

Switch(config-if)# dot1x max-req 5

Setting the Re-Authentication Number

You can also change the number of times that the switch restarts the authentication process before the port changes to the unauthorized state.

Note You should change the default value of this command only to adjust for unusual circumstances such as unreliable links or specific behavioral problems with certain clients and authentication servers.

Beginning in privileged EXEC mode, follow these steps to set the re-authentication number. This procedure is optional.

To return to the default re-authentication number, use the no dot1x max-reauth-req interface configuration command.

This example shows how to set 4 as the number of times that the switch restarts the authentication process before the port changes to the unauthorized state:

Switch(config-if)# dot1x max-reauth-req 4

Configuring the Host Mode

Beginning in privileged EXEC mode, follow these steps to allow multiple hosts (clients) on an IEEE 802.1x-authorized port that has the dot1x port-control interface configuration command set to auto. This procedure is optional.

To disable multiple hosts on the port, use the no dot1x host-mode multi-host interface configuration command.

This example shows how to enable IEEE 802.1x and to allow multiple hosts:

Switch(config)# interface gigabitethernet2/0/1

Switch(config-if)# dot1x port-control auto

Switch(config-if)# dot1x host-mode multi-host

Configuring a Guest VLAN

When you configure a guest VLAN, clients that are not IEEE 802.1x-capable are put into the guest VLAN when the server does not receive a response to its EAPOL request/identity frame. Clients that are IEEE 802.1x-capable but fail authentication are not granted access to the network. The switch supports guest VLANs in single-host or multiple-hosts mode.

Beginning in privileged EXEC mode, follow these steps to configure a guest VLAN. This procedure is optional.

To disable and remove the guest VLAN, use the no dot1x guest-vlan interface configuration command. The port returns to the unauthorized state.

This example shows how to enable VLAN 2 as an IEEE 802.1x guest VLAN:

Switch(config)# interface gigabitethernet2/0/2

Switch(config-if)# dot1x guest-vlan 2

This example shows how to set 3 as the quiet time on the switch, to set 15 as the number of seconds that the switch waits for a response to an EAP-request/identity frame from the client before resending the request, and to enable VLAN 2 as an IEEE 802.1x guest VLAN when an IEEE 802.1x port is connected to a DHCP client:

Switch(config-if)# dot1x timeout quiet-period 3

Switch(config-if)# dot1x timeout tx-period 15

Switch(config-if)# dot1x guest-vlan 2

You can enable optional guest VLAN behavior by using the dot1x guest-vlan supplicant global configuration command. When enabled, the switch does not maintain the EAPOL packet history and allows clients that fail authentication access to the guest VLAN, regardless of whether EAPOL packets had been detected on the interface.

Beginning in privileged EXEC mode, follow these steps to enable the optional guest VLAN behavior and to configure a guest VLAN. This procedure is optional.

To disable the optional guest VLAN behavior, use the no dot1x guest-vlan supplicant global configuration command. To remove the guest VLAN, use the no dot1x guest-vlan interface configuration command. The port returns to the unauthorized state.

This example shows how enable the optional guest VLAN behavior and to specify VLAN 5 as an IEEE 802.1x guest VLAN:

Switch(config)# dot1x guest-vlan supplicant

Switch(config)# interface gigabitethernet2/0/1

Switch(config-if)# dot1x guest-vlan 5

Resetting the IEEE 802.1x Configuration to the Default Values

Beginning in privileged EXEC mode, follow these steps to reset the IEEE 802.1x configuration to the default values. This procedure is optional.

Configuring IEEE 802.1x Accounting

Enabling AAA system accounting with IEEE 802.1x accounting allows system reload events to be sent to the accounting RADIUS server for logging. The server can then infer that all active IEEE 802.1x sessions are closed.

Because RADIUS uses the unreliable UDP transport protocol, accounting messages might be lost due to poor network conditions. If the switch does not receive the accounting response message from the RADIUS server after a configurable number of retransmissions of an accounting request, this system message appears:

Accounting message %s for session %s failed to receive Accounting Response.

When the stop message is not sent successfully, this message appears:

00:09:55: %RADIUS-3-NOACCOUNTINGRESPONSE: Accounting message Start for session 
172.20.50.145 sam 11/06/03 07:01:16 11000002 failed to receive Accounting Response.

Note You must configure the RADIUS server to perform accounting tasks, such as logging start, stop, and interim-update messages and time stamps. To turn on these functions, enable logging of "Update/Watchdog packets from this AAA client" in your RADIUS server Network Configuration tab. Next, enable "CVS RADIUS Accounting" in your RADIUS server System Configuration tab.

Beginning in privileged EXEC mode, follow these steps to configure IEEE 802.1x accounting after AAA is enabled on your switch. This procedure is optional.

Use the show radius statistics privileged EXEC command to display the number of RADIUS messages that do not receive the accounting response message.

This example shows how to configure IEEE 802.1x accounting. The first command configures the RADIUS server, specifying 1813 as the UDP port for accounting:

Switch(config)# radius-server host 172.120.39.46 auth-port 1812 acct-port 1813 key rad123

Switch(config)# aaa accounting dot1x default start-stop group radius

Switch(config)# aaa accounting system default start-stop group radius

Displaying IEEE 802.1x Statistics and Status

To display IEEE 802.1x statistics for all ports, use the show dot1x all statistics privileged EXEC command. To display IEEE 802.1x statistics for a specific port, use the show dot1x statistics interface interface-id privileged EXEC command.

To display the IEEE 802.1x administrative and operational status for the switch, use the show dot1x all privileged EXEC command. To display the IEEE 802.1x administrative and operational status for a specific port, use the show dot1x interface interface-id privileged EXEC command.

For detailed information about the fields in these displays, see the command reference for this release.