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Configuring TACACS+ and RADIUS Extended Authentication with VPN Client

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Document ID: 12428


Contents

Introduction
Prerequisites
      Requirements
      Components Used
      Conventions
Configure
      Network Diagram
      VPN Client 1.1 Setup
      Configurations
Verify
Troubleshoot
      Troubleshooting Commands
      Sample Debug Output
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Introduction

This document shows sample configurations for TACACS+ and RADIUS Internet Engineering Task Force (IETF) Extended Authentication (Xauth). Xauth lets you deploy IP Security (IPSec) on Virtual Private Networks (VPNs) using TACACS+ or RADIUS as your user authentication method within the Internet Key Exchange (IKE) protocol. This feature provides authentication to a user who has the CiscoSecure VPN Client 1.1 installed on their PC, by prompting the user for a username and a password, and then verifies them with the information stored in the authentication, authorization, and accounting (AAA) server, the TACACS+ or RADIUS database. Authentication occurs between IKE phase 1 and IKE phase 2. If the user successfully authenticates, a phase 2 Security Association (SA) is established after which data can be sent securely to the protected network.

Xauth includes authentication only, not authorization (where users can go once the connection is established). Accounting (where users went) is not implemented.

The configuration must work without Xauth before implementing Xauth. Our example demonstrates Mode Configuration (Mode Config) and Network Address Translation (NAT) in addition to Xauth, but the assumption is that IPSec connectivity is present before adding the Xauth commands.

Make sure that local Xauth (username/password on the router) works before attempting TACACS+ or RADIUS Xauth.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document is based on these software and hardware versions:

  • VPN Client Version 1.1 (or later)

  • Cisco IOS® Releases 12.1.2.2.T, 12.1.2.2.P (or later)

  • RADIUS authentication was tested with Cisco 3640 running c3640-jo3s56i-mz.121-2.3.T

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

Refer to the Cisco Technical Tips Conventions for more information on document conventions.

Configure

In this section, you are presented with the information to configure the features described in this document.

Note: Use the Command Lookup Tool ( registered customers only) to obtain more information on the commands used in this section.

Network Diagram

This document uses this network setup:

xauthTR.gif

VPN Client 1.1 Setup 

Network Security policy: 
 1- Myconn 
         My Identity = ip address
                 Connection security: Secure 
                 Remote Party Identity and addressing 
                         ID Type: IP subnet 
                         10.13.1.0 (range of inside network)
                         Port all Protocol all 

                 Connect using secure tunnel 
                         ID Type: IP address 
                         99.99.99.1
                         Pre-shared key = cisco1234

         Authentication (Phase 1) 
         Proposal 1 
                 Authentication method: pre-shared key 
                 Encryp Alg: DES 
                 Hash Alg: MD5 
                 SA life: Unspecified
                 Key Group: DH 1 

         Key exchange (Phase 2) 
         Proposal 1 
                 Encapsulation ESP 
                 Encrypt Alg: DES 
                 Hash Alg: MD5 
                 Encap: tunnel 
                 SA life: Unspecified 
                 no AH 

 2- Other Connections 
             Connection security: Non-secure 
             Local Network Interface 
                 Name: Any 
                 IP Addr: Any 
                 Port: All

With Xauth enabled on the router, when the user tries to connect to a device inside the router (here we did a ping -t #.#.#.#), a grey screen comes up: 

User Authentication for 3660
Username:
Password:

Configurations

Server Configuration

Xauth authentication can be done by either TACACS+ or by RADIUS. We wanted to be sure that the Xauth users were allowed to do Xauth, but not allowed to telnet to the router, so we added the aaa authorization exec command. We gave the RADIUS users "reply-attribute Service-Type=Outbound=5" (instead of Administrative or Login). In CiscoSecure UNIX, this is "Outbound"; in CiscoSecure NT this is "Dialout Framed." If these were TACACS+ users, we would not give them shell/exec permissions.

Router Configuration for TACACS+ or RADIUS Xauth

 
Current configuration:
!
version 12.1
service timestamps debug uptime
service timestamps log uptime
no service password-encryption
!
hostname carter
!

!--- Enable AAA and define authentication and authorization parameters

aaa new-model
aaa authentication login default group radius|tacacs+ none
aaa authentication login xauth_list group radius|tacacs+
aaa authorization exec default group radius|tacacs+ none 
enable secret 5 $1$VY18$uO2CRnqUzugV0NYtd14Gg0
enable password ww
!
username john password 0 doe
!
ip subnet-zero
ip audit notify log
ip audit po max-events 100
cns event-service server
!
crypto isakmp policy 10
hash md5
authentication pre-share
crypto isakmp key cisco1234 address 0.0.0.0 0.0.0.0
crypto isakmp client configuration address-pool local ourpool
!
crypto ipsec transform-set mypolicy esp-des esp-md5-hmac 
!
crypto dynamic-map dyna 10
set transform-set mypolicy 
!
crypto map test client authentication list xauth_list
crypto map test client configuration address initiate
crypto map test client configuration address respond
crypto map test 5 ipsec-isakmp dynamic dyna 
!
interface Ethernet0/0
ip address 10.13.1.48 255.255.255.0
ip nat inside
no ip route-cache
no ip mroute-cache
no mop enabled
!
interface TokenRing0/0
no ip address
shutdown
ring-speed 16
!
interface Ethernet2/0
ip address 99.99.99.1 255.255.255.0
ip nat outside
no ip route-cache
no ip mroute-cache
no mop enabled
crypto map test
!
interface TokenRing2/0
no ip address
shutdown
ring-speed 16
!
ip local pool ourpool 10.2.1.1 10.2.1.254
ip nat pool outsidepool 99.99.99.50 99.99.99.60 netmask 255.255.255.0
ip nat inside source route-map nonat pool outsidepool
ip classless
ip route 0.0.0.0 0.0.0.0 10.13.1.1
no ip http server
!
access-list 101 deny ip 10.13.1.0 0.0.0.255 10.2.1.0 0.0.0.255
access-list 101 permit ip 10.13.1.0 0.0.0.255 any
dialer-list 1 protocol ip permit
dialer-list 1 protocol ipx permit
route-map nonat permit 10
match ip address 101
!

!--- Define TACACS server host and key parameters

tacacs-server host 172.18.124.114
tacacs-server key cisco
radius-server host 172.18.124.114 auth-port 1645 acct-port 1646
radius-server retransmit 3
radius-server key cisco
!
line con 0
transport input none
line aux 0
line vty 0 4
password WW
!
end

Verify

There is currently no verification procedure available for this configuration.

Troubleshoot

This section provides information you can use to troubleshoot your configuration.

Troubleshooting Commands

The Output Interpreter Tool ( registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.

Note: Refer to Important Information on Debug Commands before you use debug commands.

  • debug aaa authentication—Displays information on AAA/TACACS+ authentication.

  • debug crypto isakmp—Displays messages about IKE events.

  • debug crypto ipsec—Displays IPSec events.

  • debug crypto key-exchange—Shows Digital Signature Standard (DSS) public key exchange messages.

  • debug radius—Displays information associated with RADIUS.

  • debug tacacs—Displays information associated with the TACACS.

  • clear crypto isakmp—Specifies which connection to clear.

  • clear crypto sa—Deletes IPSec security associations.

Sample Debug Output

Note: TACACS+ debug would be very similar. Use the debug tacacs+ command instead of the debug radius command.

Carter#show debug
General OS:
  AAA Authentication debugging is on
Radius protocol debugging is on
Cryptographic Subsystem:
  Crypto ISAKMP debugging is on
  Crypto Engine debugging is on
  Crypto IPSEC debugging is on
Carter#term mon
03:12:54: ISAKMP (0:0): received packet from 99.99.99.5 (N) NEW SA
03:12:54: ISAKMP: local port 500, remote port 500
03:12:54: ISAKMP (0:1): Setting client config settings 6269C36C
03:12:54: ISAKMP (0:1): (Re)Setting client xauth list xauth_list 
   and state
03:12:54: ISAKMP: Created a peer node for 99.99.99.5
03:12:54: ISAKMP: Locking struct 6269C36C from 
   crypto_ikmp_config_initialize_sa
03:12:54: ISAKMP (0:1): processing SA payload. message ID = 0
03:12:54: ISAKMP (0:1): found peer pre-shared key matching 99.99.99.5
03:12:54: ISAKMP (0:1): Checking ISAKMP transform 1 against 
   priority 10 policy
03:12:54: ISAKMP:      encryption DES-CBC
03:12:54: ISAKMP:      hash MD5
03:12:54: ISAKMP:      default group 1
03:12:54: ISAKMP:      auth pre-share
03:12:54: ISAKMP (0:1): atts are acceptable. Next payload is 0
03:12:54: CryptoEngine0: generate alg parameter
03:12:54: CRYPTO_ENGINE: Dh phase 1 status: 0
03:12:54: CRYPTO_ENGINE: DH phase 1 status: 0
03:12:54: ISAKMP (0:1): SA is doing pre-shared key authentication using 
   id type ID_IPV4_ADDR
03:12:54: ISAKMP (0:1): sending packet to 99.99.99.5 (R) MM_SA_SETUP
03:12:54: ISAKMP (0:1): received packet from 99.99.99.5 (R) MM_SA_SETUP
03:12:54: ISAKMP (0:1): processing KE payload. Message ID = 0
03:12:54: CryptoEngine0: generate alg parameter
03:12:54: ISAKMP (0:1): processing NONCE payload. Message ID = 0
03:12:54: ISAKMP (0:1): found peer pre-shared key matching 99.99.99.5
03:12:54: CryptoEngine0: create ISAKMP SKEYID for conn id 1
03:12:54: ISAKMP (0:1): SKEYID state generated
03:12:54: ISAKMP (0:1): processing vendor id payload
03:12:54: ISAKMP (0:1): processing vendor id payload
03:12:54: ISAKMP (0:1): sending packet to 99.99.99.5 (R) MM_KEY_EXCH
03:12:55: ISAKMP (0:1): received packet from 99.99.99.5 (R) MM_KEY_EXCH
03:12:55: ISAKMP (0:1): processing ID payload. Message ID = 0
03:12:55: ISAKMP (0:1): processing HASH payload. Message ID = 0
03:12:55: CryptoEngine0: generate hmac context for conn id 1
03:12:55: ISAKMP (0:1): processing NOTIFY INITIAL_CONTACT protocol 1
        spi 0, message ID = 0
03:12:55: ISAKMP (0:1): SA has been authenticated with 99.99.99.5
03:12:55: ISAKMP (1): ID payload
        next-payload : 8
        type         : 1
        protocol     : 17
        port         : 500
        length       : 8
03:12:55: ISAKMP (1): Total payload length: 12
03:12:55: CryptoEngine0: generate hmac context for conn id 1
03:12:55: CryptoEngine0: clear DH number for conn id 1
03:12:55: ISAKMP (0:1): sending packet to 99.99.99.5 (R) CONF_XAUTH   
03:12:55: ISAKMP (0:1): received packet from 99.99.99.5 (R) CONF_XAUTH   
03:12:55: ISAKMP (0:1): (Re)Setting client xauth list 
   xauth_list and state
03:12:55: ISAKMP (0:1): Need XAUTH
03:12:55: AAA: parse name=ISAKMP idb type=-1 tty=-1
03:12:55: AAA/MEMORY: create_user (0x6269AD80) user='' ruser='' 
   port='ISAKMP' rem_addr='99.99.99.5' authen_type=ASCII 
   service=LOGIN priv=0
03:12:55: AAA/AUTHEN/START (2289801324): port='ISAKMP' 
   list='xauth_list' action=LOGIN service=LOGIN
03:12:55: AAA/AUTHEN/START (2289801324): found list xauth_list
03:12:55: AAA/AUTHEN/START (2289801324): Method=radius (radius)
03:12:55: AAA/AUTHEN (2289801324): status = GETUSER
03:12:55: ISAKMP: got callback 1
03:12:55: ISAKMP/xauth: request attribute XAUTH_TYPE
03:12:55: ISAKMP/xauth: request attribute XAUTH_MESSAGE
03:12:55: ISAKMP/xauth: request attribute XAUTH_USER_NAME
03:12:55: ISAKMP/xauth: request attribute XAUTH_USER_PASSWORD
03:12:55: CryptoEngine0: generate hmac context for conn id 1
03:12:55: ISAKMP (0:1): initiating peer config to 99.99.99.5. 
   ID = -280774539
03:12:55: ISAKMP (0:1): sending packet to 99.99.99.5 (R) CONF_XAUTH   
03:13:00: ISAKMP (0:1): retransmitting phase 2 CONF_XAUTH   
    -280774539 ...
03:13:00: ISAKMP (0:1): incrementing error counter on sa: 
   retransmit phase 2
03:13:00: ISAKMP (0:1): incrementing error counter on sa: 
   retransmit phase 2
03:13:00: ISAKMP (0:1): retransmitting phase 2 -280774539 CONF_XAUTH   
03:13:00: ISAKMP (0:1): sending packet to 99.99.99.5 (R) CONF_XAUTH   
03:13:02: ISAKMP (0:1): received packet from 99.99.99.5 (R) CONF_XAUTH   
03:13:02: ISAKMP (0:1): processing transaction payload from 
   99.99.99.5. Message ID = -280774539
03:13:02: CryptoEngine0: generate hmac context for conn id 1
03:13:02: ISAKMP: Config payload REPLY
03:13:02: ISAKMP/xauth: reply attribute XAUTH_TYPE
03:13:02: ISAKMP/xauth: reply attribute XAUTH_USER_NAME
03:13:02: ISAKMP/xauth: reply attribute XAUTH_USER_PASSWORD
03:13:02: AAA/AUTHEN/CONT (2289801324): continue_login (user='(undef)')
03:13:02: AAA/AUTHEN (2289801324): status = GETUSER
03:13:02: AAA/AUTHEN (2289801324): Method=radius (radius)
03:13:02: AAA/AUTHEN (2289801324): status = GETPASS
03:13:02: AAA/AUTHEN/CONT (2289801324): continue_login (user='zeke')
03:13:02: AAA/AUTHEN (2289801324): status = GETPASS
03:13:02: AAA/AUTHEN (2289801324): Method=radius (radius)
03:13:02: RADIUS: ustruct sharecount=2
03:13:02: RADIUS: Initial Transmit ISAKMP id 29 172.18.124.114:1645, 
   Access-Request, len 68
03:13:02:         Attribute 4 6 0A0D0130
03:13:02:         Attribute 61 6 00000000
03:13:02:         Attribute 1 6 7A656B65
03:13:02:         Attribute 31 12 39392E39
03:13:02:         Attribute 2 18 D687A79D
03:13:02: RADIUS: Received from id 29 172.18.124.114:1645, 
   Access-Accept, Len 26
03:13:02:         Attribute 6 6 00000005
03:13:02: RADIUS: saved authorization data for user 6269AD80 
   at 62634D0C
03:13:02: AAA/AUTHEN (2289801324): status = PASS
03:13:02: ISAKMP: got callback 1
03:13:02: CryptoEngine0: generate hmac context for conn id 1
03:13:02: ISAKMP (0:1): initiating peer config to 99.99.99.5. 
   ID = -280774539
03:13:02: ISAKMP (0:1): sending packet to 99.99.99.5 (R) CONF_XAUTH   
03:13:03: ISAKMP (0:1): received packet from 99.99.99.5 (R) CONF_XAUTH   
03:13:03: ISAKMP (0:1): processing transaction payload from 99.99.99.5. 
   Message ID = -280774539
03:13:03: CryptoEngine0: generate hmac context for conn id 1
03:13:03: ISAKMP: Config payload ACK
03:13:03: ISAKMP (0:1): deleting node -280774539 error FALSE 
   reason "done with transaction"
03:13:03: ISAKMP (0:1): allocating address 10.2.1.2
03:13:03: CryptoEngine0: generate hmac context for conn id 1
03:13:03: ISAKMP (0:1): initiating peer config to 99.99.99.5. 
   ID = 2130856112
03:13:03: ISAKMP (0:1): sending packet to 99.99.99.5 (R) CONF_ADDR    
03:13:03: ISAKMP (0:1): received packet from 99.99.99.5 (R) CONF_ADDR    
03:13:03: ISAKMP (0:1): processing transaction payload 
   from 99.99.99.5. Message ID = 2130856112
03:13:03: CryptoEngine0: generate hmac context for conn id 1
03:13:03: ISAKMP: Config payload ACK
03:13:03: ISAKMP (0:1): peer accepted the address!
03:13:03: ISAKMP (0:1): adding static route for 10.2.1.2
03:13:03: ISAKMP (0:1): installing route 10.2.1.2 255.255.255.255 
   99.99.99.5
03:13:03: ISAKMP (0:1): deleting node 2130856112 error FALSE 
   reason "done with transaction"
03:13:03: ISAKMP (0:1): Delaying response to QM request.
03:13:04: ISAKMP (0:1): received packet from 99.99.99.5 (R) QM_IDLE      
03:13:04: ISAKMP (0:1): (Re)Setting client xauth list xauth_list 
   and state
03:13:04: CryptoEngine0: generate hmac context for conn id 1
03:13:04: ISAKMP (0:1): processing HASH payload. Message ID = -1651205463
03:13:04: ISAKMP (0:1): processing SA payload. Message ID = -1651205463
03:13:04: ISAKMP (0:1): Checking IPSec proposal 1
03:13:04: ISAKMP: transform 1, ESP_DES
03:13:04: ISAKMP:   attributes in transform:
03:13:04: ISAKMP:      authenticator is HMAC-MD5
03:13:04: ISAKMP:      encaps is 1
03:13:04: validate proposal 0
03:13:04: ISAKMP (0:1): atts are acceptable.
03:13:04: IPSEC(validate_proposal_request): proposal part #1,
  (key eng. msg.) dest= 99.99.99.1, src= 99.99.99.5, 
    dest_proxy= 10.13.1.0/255.255.255.0/0/0 (type=4), 
    src_proxy= 10.2.1.2/255.255.255.255/0/0 (type=1),
    protocol= ESP, transform= ESP-Des esp-md5-hmac , 
    lifedur= 0s and 0kb, 
    spi= 0x0(0), conn_id= 0, keysize= 0, flags= 0x4
03:13:04: validate proposal request 0
03:13:04: ISAKMP (0:1): processing NONCE payload. 
   Message ID = -1651205463
03:13:04: ISAKMP (0:1): processing ID payload. 
   Message ID = -1651205463
03:13:04: ISAKMP (1): ID_IPV4_ADDR src 10.2.1.2 prot 0 port 0
03:13:04: ISAKMP (0:1): processing ID payload. 
   Message ID = -1651205463
03:13:04: ISAKMP (1): ID_IPV4_ADDR_SUBNET dst 10.13.1.0/255.255.255.0 
   port 0 port 0
03:13:04: ISAKMP (0:1): asking for 1 spis from ipsec
03:13:04: IPSEC(key_engine): got a queue event...
03:13:04: IPSEC(spi_response): getting spi 570798685 for SA 
        from 99.99.99.5      to 99.99.99.1      for prot 3
03:13:04: ISAKMP: received ke message (2/1)
03:13:04: CryptoEngine0: generate hmac context for conn id 1
03:13:04: ISAKMP (0:1): sending packet to 99.99.99.5 (R) QM_IDLE      
03:13:04: ISAKMP (0:1): received packet from 99.99.99.5 (R) QM_IDLE      
03:13:04: CryptoEngine0: generate hmac context for conn id 1
03:13:04: ipsec allocate flow 0
03:13:04: ipsec allocate flow 0
03:13:04: ISAKMP (0:1): Creating IPSec SAs
03:13:04:         inbound SA from 99.99.99.5 to 99.99.99.1
        (proxy 10.2.1.2 to 10.13.1.0)
03:13:04:         has spi 0x2205B25D and conn_id 2000 and flags 4
03:13:04:         outbound SA from 99.99.99.1 to 99.99.99.5      
   (proxy 10.13.1.0 to 10.2.1.2)
03:13:04:         has spi -1338747879 and conn_id 2001 and flags 4
03:13:04: ISAKMP (0:1): deleting node -195511155 error FALSE 
   reason "saved qm no longer needed"
03:13:04: ISAKMP (0:1): deleting node -1651205463 error FALSE 
   reason "quick mode done (await()"
03:13:04: IPSEC(key_engine): got a queue event...
03:13:04: IPSEC(initialize_sas): ,
  (key eng. msg.) dest= 99.99.99.1, src= 99.99.99.5, 
    dest_proxy= 10.13.1.0/255.255.255.0/0/0 (type=4), 
    src_proxy= 10.2.1.2/0.0.0.0/0/0 (type=1),
    protocol= ESP, transform= esp-des esp-md5-hmac , 
    lifedur= 0s and 0kb, 
    spi= 0x2205B25D(570798685), conn_id= 2000, 
    keysize= 0, flags= 0x4
03:13:04: IPSEC(initialize_sas): ,
  (key eng. msg.) src= 99.99.99.1, dest= 99.99.99.5, 
    src_proxy= 10.13.1.0/255.255.255.0/0/0 (type=4), 
    dest_proxy= 10.2.1.2/0.0.0.0/0/0 (type=1),
    protocol= ESP, transform= esp-des esp-md5-hmac , 
    lifedur= 0s and 0kb, 
    spi= 0xB0345419(2956219417), conn_id= 2001, 
    keysize= 0, flags= 0x4
03:13:04: IPSEC(create_sa): sa created,
  (sa) sa_dest= 99.99.99.1, sa_prot= 50, 
    sa_spi= 0x2205B25D(570798685), 
    sa_trans= esp-des esp-md5-hmac , sa_conn_id= 2000
03:13:04: IPSEC(create_sa): sa created,
  (sa) sa_dest= 99.99.99.5, sa_prot= 50, 
    sa_spi= 0xB0345419(2956219417), 
    sa_trans= esp-des esp-md5-hmac , sa_conn_id= 2001
03:13:04: ISAKMP: received ke message (4/1)
03:13:04: ISAKMP: Locking struct 6269C36C for IPSEC
03:13:05: IPSEC(decapsulate): error in decapsulation 
   crypto_ipsec_sa_exists

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Related Information

Updated: Jan 21, 2005Document ID: 12428