Cisco IOS Security Configuration Guide: Securing User Services, Release 12.4

RADIUS EAP Support

The RADIUS EAP Support feature makes it possible for users to apply the client authentication methods within PPP (including proprietary authentication), which may not be supported by the network access server (NAS); to be accomplished through the Extensible Authentication Protocol (EAP). Before this feature was introduced, support for various authentication methods for PPP connections required custom vendor-specific configuration and changes to the client and NAS. RADIUS EAP support allows authentication schemes, such as token cards and public key, to strengthen end-user and device authenticated access to their networks.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for RADIUS EAP Support" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp. An account on Cisco.com is not required.

Contents

•Prerequisites for RADIUS EAP Support

•Restrictions for RADIUS EAP Support

•Information About RADIUS EAP Support

•How to Configure RADIUS EAP Support

•Configuration Examples

•Additional References

•Feature Information for RADIUS EAP Support

•Glossary

Prerequisites for RADIUS EAP Support

Before enabling EAP RADIUS on the client, you must perform the following tasks:

•Configure an interface type and enter interface configuration mode by using the interface command.

•Configure the interface for PPP encapsulation by using the encapsulation command.

For more information on completing these tasks, refer to the "Configuring Asynchronous SLIP and PPP" module.

Restrictions for RADIUS EAP Support

When EAP is running in proxy mode, there may be a significant increase in the authentication time because every packet from the peer must be sent to the RADIUS server and every EAP packet from the RADIUS server must be sent back to the client. Although this extra processing causes delays, you can increase the default authentication timeout value by using the ppp timeout authentication command.

Information About RADIUS EAP Support

EAP is an authentication protocol for PPP that supports multiple authentication mechanisms that are negotiated during the authentication phase (instead of the link control protocol [LCP] phase). EAP allows a third-party authentication server to interact with a PPP implementation through a generic interface.

How EAP Works

By default, EAP runs in proxy mode. This means that EAP allows the entire authentication process to be negotiated by the NAS to a back-end server that may reside on or be accessed through a RADIUS server. After EAP is negotiated between the client and the NAS during LCP exchange, all further authentication messages are transparently transmitted between the client and the back-end server. The NAS is no longer directly involved in the authentication process; that is, the NAS works as a proxy, sending EAP messages between the remote peers.

Note EAP can also run in a local mode; the session is authenticated using the Message Digest 5 (MD5) algorithm and obeys the same authentication rules as Challenge Handshake Authentication Protocol (CHAP). To disable proxy mode and authenticate locally, you must use the ppp eap local command.

Newly Supported Attributes

The RADIUS EAP Support feature introduces support for the following RADIUS attributes

:

How to Configure RADIUS EAP Support

See the following sections for configuration tasks for the RADIUS EAP Support feature. Each task in the list is identified as either required or optional.

•Configuring EAP (required)

•Verifying EAP (optional)

Configuring EAP

Perform this task to configure EAP on an interface configured for PPP encapsulation.

SUMMARY STEPS

1. enable

2. configure terminal

3. ppp authentication eap

4. ppp eap identity string

5. ppp eap password [number] string

6. ppp eap local

7. ppp eap wait

8. ppp eap refuse [callin]

DETAILED STEPS

Verifying EAP

To verify EAP configurations on your client or NAS, use at least one of the following commands in privileged EXEC configuration mode:

Configuration Examples

This section provides the following configuration examples:

•EAP Local Configuration on Client: Example

•EAP Proxy Configuration for NAS: Example

EAP Local Configuration on Client: Example

The following example is a sample configuration for a client configured for EAP:

interface Ethernet0/0

 ip address 10.1.1.202 255.255.255.0

 no ip mroute-cache

 half-duplex

!

interface BRI0/0

 ip address 192.168.101.100 255.255.255.0

 encapsulation ppp

 no ip mroute-cache

 dialer map ip 192.168.101.101 56167

 dialer-group 1

 isdn switch-type basic-5ess

 ppp eap identity user

 ppp eap password 7 141B1309

!

!

ip default-gateway 10.1.1.1

ip classless

ip route 192.168.101.101 255.255.255.255 BRI0/0

no ip http server

!

dialer-list 1 protocol ip permit

EAP Proxy Configuration for NAS: Example

The following example is a sample configuration for a NAS configured to use EAP proxy:

aaa authentication login default group radius

aaa authentication login NOAUTH none

aaa authentication ppp default if-needed group radius

aaa session-id common

enable secret 5 $1$x5D0$cfTL/D8Be.34PgTbdGdgl/

!

username dtw5 password 0 lab

username user password 0 lab

ip subnet-zero

no ip domain-lookup

ip host lab24-boot 172.19.192.254

ip host lb 172.19.192.254

!

isdn switch-type primary-5ess

!

controller T1 3

 framing esf

 linecode b8zs

 pri-group timeslots 1-24 

!

interface Ethernet0

 ip address 10.1.1.108 255.255.255.0

 no ip route-cache

 no ip mroute-cache

!

interface Serial3:23

 ip address 192.168.101.101 255.255.255.0

 encapsulation ppp

 dialer map ip 192.168.101.100 60213

 dialer-group 1

 isdn switch-type primary-5ess

 isdn T321 0

 ppp authentication eap

 ppp eap password 7 011F0706

!

!

ip default-gateway 10.0.190.1

ip classless

ip route 192.168.101.0 255.255.255.0 Serial3:23

no ip http server

!

dialer-list 1 protocol ip permit

!

radius-server host 10.1.1.201 auth-port 1645 acct-port 1646 key lab

radius-server retransmit 3

call rsvp-sync

!

mgcp profile default

!

!

line con 0

 exec-timeout 0 0

 logging synchronous

 login authentication NOAUTH

line 1 48

line aux 0

ine vty 0 4

lpassword lab

Additional References

The following sections provide references related to RADIUS EAP Support feature.

Related Documents

Standards

MIBs

RFCs

Technical Assistance

Feature Information for RADIUS EAP Support

Table 1 lists the release history for this feature.

Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp. An account on Cisco.com is not required.

Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature.

Glossary

attribute—A RADIUS Internet Engineering Task Force (IETF) attribute is one of the original set of 255 standard attributes that are used to communicate authentication, authorization, and accounting (AAA) information between a client and a server. Because IETF attributes are standard, the attribute data is predefined and well known; thus all clients and servers that exchange AAA information through IETF attributes must agree on attribute data such as the exact meaning of the attributes and the general bounds of the values for each attribute.

CHAP—Challenge Handshake Authentication Protocol. Security feature that is supported on lines using PPP encapsulation and prevents unauthorized access. CHAP does not itself prevent unauthorized access; it merely identifies the remote end. The router or access server then determines whether that user is allowed access.

EAP—Extensible Authentication Protocol. A PPP authentication protocol that supports multiple authentication mechanisms that are negotiated during the authentication phase (instead of the Link Control Protocol [LCP] phase). EAP allows a third-party authentication server to interact with the PPP implementation through a generic interface.

LCP—link control protocol. Protocol that establishes, configures, and tests data-link connections for use by PPP.

MD5 (HMAC variant)—Message Digest 5. A hash algorithm used to authenticate packet data. HMAC is a key hashing for message authentication.

NAS—network access server. A device providing local network access to users across a remote access network such as the public switched telephone network (PSTN).

PAP—Password Authentication Protocol. Authentication protocol that allows PPP peers to authenticate one another. The remote router attempting to connect to the local router is required to send an authentication request. Unlike CHAP, PAP passes the password and host name or username in the clear (unencrypted). PAP does not itself prevent unauthorized access; it merely identifies the remote end. The router or access server then determines if that user is allowed access. PAP is supported only on PPP lines.

PPP—Point-to-Point Protocol. A protocol that encapsulates network layer protocol information over point-to-point links. PPP is defined in RFC 1661.

RADIUS—Remote Authentication Dial-In User Service. Database for authenticating modem and ISDN connections and for tracking connection time.

Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

© 2001-2009 Cisco Systems, Inc. All rights reserved.