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This document describes how Network Admission Control (NAC) works with IP Security (IPsec) Dynamic Virtual Tunnel Interface (DVTI).
TOPOLOGY
The network topology is shown in Figure 1. The Windows client is running Cisco® VPN Client 4.0, while the Cisco 7200 hub router is running Cisco IOS® Software Release 12.4.4T using DVTI to terminate the IPsec connections. NAC is applied on the virtual template, and Cisco Secure Access Control Server (ACS) 3.3 is used as the authentication, authorization, and accounting (AAA) server for IPsec and NAC.
Figure 1. Network Topology
INITIAL SETUP
The PC running Cisco VPN Client 4.0 connects to the DVTI hub, and Internet Key Exchange (IKE) Authorization, Xauth and Mode-Config are completed through exchanges with the AAA server. Once the IPsec security associations (SA) are up, a virtual access interface is cloned from the DVTI virtual template. We have applied access control list (ACL) and NAC statements on the virtual template, which are inherited by the virtual access interface. The hub kicks off eopoudp authentication with the client, and exchanges eop over radius messages with the AAA server. The resulting PEAP session between client and AAA server is used to gather the Clients' posture. The client is running Cisco Trust Agent and sends its posture. The AAA server uses this posture for health assessment of the Client and sends appropriate access accept/reject messages to the hub.
In this sample test scenario, the posture validation is done based on the client OS string. Based on the posture, the RADIUS server sends an ACL (first sends ACL name, then hub gets the actual ACL) to the hub router. The hub router applies the ACL on the virtual access interface, allowing the client to send traffic to the corporate network, if it is healthy
In this scenario, the RADIUS server is Cisco Secure ACS 3.3, and is used for IPsec (IKE authorization, Xauth, and Mode-Cfg) and also for NAC. The minimum IPsec AAA attributes like IP Address, Preshared Keys etc are used. For more information on Easy VPN server and IPSec Radius attributes, please refer to: http://www.cisco.com/en/US/products/ps6350/products_configuration_guide_chapter09186a0080455b6a.html
The NAC setup is rudimentary in this test example. The client is not running any antivirus software. Posture validation is based on the client OS string-if it contains "Windows" it is defined as healthy and an `ip any any' ACL is pushed down to be applied to the virtual access interface. For more NAC deployment scenarios, please refer to the NAC documentation at: http://www.cisco.com/en/US/netsol/ns466/networking_solutions_package.html
DVTI AND NAC CONFIGURATION
The DVTI and NAC configuration is shown below:
crypto isakmp profile nac
match identity group nac
client authentication list VPN-AAA
isakmp authorization list VPN-AAA
client configuration address respond
virtual-template 1
!
interface Virtual-Template1 type tunnel
ip unnumbered Loopback10
ip access-group 101 in
ip admission vti-nac
load-interval 30
tunnel mode ipsec ipv4
tunnel protection ipsec profile nac
!
access-list 101 permit udp any any eq 21862
CONFIGURING CISCO SECURE ACS 3.3
Cisco Secure ACS Version
Figure 2 shows the ACS version information.
Figure 2. ACS Version
IPsec Group Attributes
EzVPN Groupname = nac
Figure 3 shows the IPSec Group attributes defined on ACS.
Figure 3. IPSec Group Attributes
IPsec Xauth Username
Username = sunil
Figure 4 shows the username and password defined for the vpn client.
Figure 4. IPSec Xauth Username
Defining NAC External Database for Posture Validation
We define a Validation Policy that says a posture with an OS string containing "Windows" is declared as "healthy". Figure 5 shows the ACS External database definitions.
Figure 5. ACS External Database
Figure 6 shows the ACS External Databases. Pick "Network Admission Control."
Figure 6. ACS External Database
Figure 7 shows creating a new NAC database.
Figure 7. ACS NAC Database
Figure 8 shows creating the NAC Credential Validation Policies.
Figure 8. NAC Credential Policy Configuration
Figure 9 shows creating a new Policy Rule List for Client posture validation.
Figure 9. NAC Policy Rules
Defining the Unknown User Policy
Any unknown users are searched in the NAC database (Figure 10).
Figure 10. ACS Unknown User Policies
NAC Database Group Mappings
Maps the previously configure posture token "Windows" in the NAC database to the group "Healthy" (Figure 11).
Figure 11. Unknown User to NAC Database Mappings
Figure 12 shows the Group mappings for NAC Database.
Figure 12. NAC Group Mappings
Defining the User Group "Healthy"
The Healthy group is associated with an ACL to be sent to the hub router (Figure 13).
Figure 13. NAC Group Settings
Figure 14 shows the Group settings.
Figure 14. NAC Group Settings
Defining the Healthy ACL
Figure 15 shows the ACL definition.
Figure 15. NAC ACL
Figure 16 shows the ACL definition.
Figure 16. NAC ACL
Figure 17 shows the ACL definition.
Figure 17. NAC ACL
Figure 18 shows the ACL definition.
Figure 18. NAC ACL
DEBUGS AND SHOW COMMANDS
Before the Client Connects
7200-VTI-2#sh access-lists
Extended IP access list 101
10 permit udp any any eq 21862
7200-VTI-2#
While the Client Connects
Dec 7 19:11:41: RADIUS(00000014): Send Access-Request to 24.1.1.3:1645 id 1645/29, len
100
100
Dec 7 19:11:41: RADIUS: authenticator DB B1 3C 29 71 0E BD FA - 6B 46 0C ED 5C E7 96 80
Dec 7 19:11:41: RADIUS: User-Name [1] 5 "nac"
Dec 7 19:11:41: RADIUS: User-Password [2] 18 *
Dec 7 19:11:41: RADIUS: Calling-Station-Id [31] 11 "40.30.1.1"
Dec 7 19:11:41: RADIUS: NAS-Port-Type [61] 6 Virtual [5]
Dec 7 19:11:41: RADIUS: NAS-Port-Type [61] 6 Virtual [5]
Dec 7 19:11:41: RADIUS: NAS-Port [5] 6 2
Dec 7 19:11:41: RADIUS: NAS-Port-Id [87] 16 "103.121.138.76"
Dec 7 19:11:41: RADIUS: Service-Type [6] 6 Outbound [5]
Dec 7 19:11:41: RADIUS: NAS-IP-Address [4] 6 24.100.1.22
Dec 7 19:11:41: RADIUS: Received from id 1645/29 24.1.1.3:1645, Access-Accept, len 148
Dec 7 19:11:41: RADIUS: authenticator DC D3 E6 DB 06 39 D8 08 - 5D EA 7F 13 00 56 22 48
Dec 7 19:11:41: RADIUS: Vendor, Cisco [26] 30
Dec 7 19:11:41: RADIUS: Cisco AVpair [1] 24 "ipsec:key-exchange=ike"
Dec 7 19:11:41: RADIUS: Vendor, Cisco [26] 36
Dec 7 19:11:41: RADIUS: Cisco AVpair [1] 30 "ipsec:tunnel-password=nac123"
Dec 7 19:11:41: RADIUS: Vendor, Cisco [26] 32
Dec 7 19:11:41: RADIUS: Cisco AVpair [1] 26 "ipsec:addr-pool=nac-pool"
Dec 7 19:11:41: RADIUS: Class [25] 30
Dec 7 19:11:53: RADIUS(00000015): Send Access-Request to 24.1.1.3:1645 id 1645/30, len 90
Dec 7 19:11:53: RADIUS: authenticator 76 EF D8 81 87 92 55 2C - 06 47 2F 2C 65 48 52 EF
Dec 7 19:11:53: RADIUS: User-Name [1] 7 "sunil"
Dec 7 19:11:53: RADIUS: User-Pass:53: RADIUS: 61 2F 31 38 36 34 30 31 31 36 2F 32
[a/18640116/2]
[a/18640116/2]
Dec 7 19:11:53: RADIUS(00000015): Received from id 1645/30
AAA/AUTHOR/IKE: Processing AV addr
Dec 7 19:11:53: ISAKMP:(13006):AAA Authen: No group atts addedword
Dec 7 19:11:53: %CRYPTO-6-VPN_TUNNEL_STATUS: (Server) Authentication PASSED User=sunil
Group=nac Client_public_addr=40.30.1.1 Server_public_addr=40.22.1.1 [2] 18 *
Group=nac Client_public_addr=40.30.1.1 Server_public_addr=40.22.1.1 [2] 18 *
Dec 7 19:11:53: RADIUS: C
Dec 7 19:11:53: ISAKMP:(13006):ISAKMP/author: setting up the authorization request for
nac
nac
Dec 7 19:11:53: %CRYPTO-5-SESSION_STATUS: Crypto tunnel is UP . Peer 40.30.1.1:500
Id: nac 7 19:
Id: nac 7 19:
Dec 7 19:11:53: %CRYPTO-6-EZVPN_CONNECTION_UP: (Server) Mode=CLIENT_OR_NEM_PLUS
Client_type=UNKNOWN User=sunil Group=nac Client_public_addr=40.30.1.1
Server_public_addr=40.22.1.1 Assigned_client_addr=192.168.1.4 11:
Client_type=UNKNOWN User=sunil Group=nac Client_public_addr=40.30.1.1
Server_public_addr=40.22.1.1 Assigned_client_addr=192.168.1.4 11:
Dec 7 19:11:54: %LINEPROTO-5-UPDOWN: Line protocol on Interface Virtual-Access2,
RADIUS: NAS-Port-OU Init Validation for idb= Virtual-Access2 src_mac= 0000.7f11.6a5a
src_ip= 192.168.1.4
src_ip= 192.168.1.4
Dec 7 19:11:54: eou-ev:30.3.143.24: msg = 33(eventEouCreateSession)
Dec 7 19:11:54: AAA/BIND(00000016): Bind i/f
Dec 7 19:11:54: eou_auth 192.168.1.4: initial state eou_initialize has enter
Dec 7 19:11:54: eou-obj_create:192.168.1.4: EAPoUDP Session Created
Dec 7 19:11:54: eou-obj_link:192.168.1.4: EAPoUDP Session added to Hash tableType
[61]
[61]
Dec 7 19:11:54: %EOU-6-SESSION: IP=192.168.1.4| HOST=DETECTED| Interface=Virtual-Access2
6 Vir
6 Vir
Dec 7 19:11:54: eou_auth 192.168.1.4: during state eou_initialize, got event
1(eouCheckProfile)
1(eouCheckProfile)
Dec 7 19:11:54: @@@ eou_auth 192.168.1.4: eou_initialize -> eou_initialize
Dec 7 19:11:54: eou-ev:192.168.1.4: msg = 3(eventEouStartHello)
Dec 7 19:11:54: eou_auth 192.168.1.4: during state eou_initialize, got event
3(eouStartHello)
3(eouStartHello)
Dec 7 19:11:54: @@@ eou_auth 192.168.1.4: eou_initialize -> eou_hello
Dec 7 19:11:54: eou-ev:Starting Retransmit timer 3(192.168.1.4)
Dec 7 19:11:54: eou-ev:eou_send_hello_request: Send Hello Request host= 10.1.1.1
eou_port= 5566 (hex)
eou_port= 5566 (hex)
Dec 7 19:11:54: TLV M:1 R:0 Type=ASSOCIATION ID Length=4 Association=-864887300
Dec 7 19:11:54: eou_auth 192.168.1.4: during state eou_hello, got event
5(eouHelloResponse) [5]
5(eouHelloResponse) [5]
Dec 7 19:11:54: @@@ eou_auth 192.168.1.4: eou_hello -> eou_client19:11:5
Dec 7 19:11:54: %EOU-6-CTA: IP=192.168.1.4| CiscoTrustAgent=DETECTED3: RADIUS: NAS-Port
[5] 6 2
[5] 6 2
Dec 7 19:11:53: RADIUS: NAS-Port-Id [87] 16 "103.121.138.76"
Dec 7 19:11:53: RADIUS: NAS-IP-Address [4] 6 24.100.1.22
Dec 7 19:11:53: RADIUS: Received from id 1645/30 24.1.1.3:1645, Access-Accept, len 56
Dec 7 19:12:00: RADIUS: Service-Type [6] 6 EAPoUDP [25]
Dec 7 19:12:00: RADIUS: NAS-IP-Address [4] 6 24.100.1.22
Dec 7 19:12:00: RADIUS: Received from id 1645/40 24.1.1.3:1645, Access-Accept, len 327
Dec 7 19:12:00: RADIUS: authenticator C1 BC 26 5A A6 D5 F3 83 - 50 F7 43 FC EC 36 65 A0
Dec 7 19:12:00: RADIUS: Session-Timeout [27] 6 300
Dec 7 19:12:00: RADIUS: NAS-IP-Address [4] 6 24.100.1.22
Dec 7 19:12:00: EAPoUDP (rx) Flags:128 Ver=1 opcode=4 Len=0 MsgId=3140505256 Assoc
ID=3120086995
ID=3120086995
Dec 7 19:12:00: eou_auth 192.168.1.4: during state eou_authenticated, got event
7(eouResultAck)
7(eouResultAck)
Dec 7 19:12:00: @@@ eou_auth 192.168.1.4: eou_authenticated -> eou_authenticated
Dec 7 19:12:00: eou-ev:Starting Status Query timer 300(192.168.1.4)
Dec 7 19:12:00: RADIUS: Received from id 1645/41 24.1.1.3:1645, Access-Accept, len 128
After IPSec Connection Is Up
7200-VTI-2# sh cry isa sa de
Codes: C - IKE configuration mode, D - Dead Peer Detection
K - Keepalives, N - NAT-traversal
X - IKE Extended Authentication
psk - Preshared key, rsig - RSA signature
renc - RSA encryption
IPv4 Crypto ISAKMP SA
C-id Local Remote I-VRF Status Encr Hash Auth DH Lifetime Cap.
13006 40.22.1.1 40.30.1.1 ACTIVE 3des sha 2 05:57:41 CDX
Engine-id:Conn-id = VAM2+:6
7200-VTI-2#
7200-VTI-2# sh access-li
Extended IP access list 101
permit ip host 192.168.1.4 any (53 matches)
10 permit udp any any eq 21862 (33 matches)
Extended IP access list xACSACLx-IP-hea-42f77dc1
10 permit ip any any
7200-VTI-2#
7200-VTI-2# sh eou all
------------------------------------------------------------------
Address Interface AuthType Posture-Token Age(min)
------------------------------------------------------------------
192.168.1.4 Virtual-Access2 EAP Healthy 2
7200-VTI-2#
7200-VTI-2# sh eou ip 192.168.1.4
Address : 192.168.1.4
Interface : Virtual-Access2
AuthType : EAP
PostureToken : Healthy
Age(min) : 2
URL Redirect : NO URL REDIRECT
ACL Name : #ACSACL#-IP-hea-42f77dc1
User Name : ASWAN_2:Administrator
Revalidation Period : 300 Seconds
Status Query Period : 300 Seconds
Current State : AUTHENTICATED
7200-VTI-2#
7200-VTI-2# sh run int virtual-template 1
Building configuration...
Current configuration : 198 bytes
!
interface Virtual-Template1 type tunnel
ip unnumbered Loopback10
ip access-group 101 in
ip admission vti-nac
load-interval 30
tunnel mode ipsec ipv4
tunnel protection ipsec profile nac
end
7200-VTI-2#
7200-VTI-2# sh run int virtual-access 2
Building configuration...
Current configuration : 286 bytes
!
interface Virtual-Access2
mtu 1514
ip unnumbered Loopback10
ip access-group 101 in
ip admission vti-nac
load-interval 30
tunnel source 40.22.1.1
tunnel destination 40.30.1.1
tunnel mode ipsec ipv4
tunnel protection ipsec profile nac
no tunnel protection ipsec initiate
end
7200-VTI-2#
7200-VTI-2# sh int virtual-access 2
Virtual-Access2 is up, line protocol is up
Hardware is Virtual Access interface
Interface is unnumbered. Using address of Loopback10 (10.1.1.1)
MTU 1514 bytes, BW 9 Kbit, DLY 500000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation TUNNEL
Tunnel vaccess, cloned from Virtual-Template1
Vaccess status 0x4, loopback not set
Keepalive not set
Tunnel source 40.22.1.1, destination 40.30.1.1
Tunnel protocol/transport IPSEC/IP
Tunnel TTL 255
Fast tunneling enabled
Tunnel transmit bandwidth 8000 (kbps)
Tunnel receive bandwidth 8000 (kbps)
Tunnel protection via IPsec (profile "nac")
Last input never, output never, output hang never
Last clearing of "show interface" counters 00:05:41
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/0 (size/max)
30 second input rate 0 bits/sec, 0 packets/sec
30 second output rate 0 bits/sec, 0 packets/sec
70 packets input, 8234 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
22 packets output, 2616 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
7200-VTI-2#
7200-VTI-2# sh cry ips sa
interface: Virtual-Access2
Crypto map tag: Virtual-Access2-head-0, local addr 40.22.1.1
protected vrf: (none)
local ident (addr/mask/prot/port): (0.0.0.0/0.0.0.0/0/0)
remote ident (addr/mask/prot/port): (192.168.1.4/255.255.255.255/0/0)
current_peer 40.30.1.1 port 500
PERMIT, flags={origin_is_acl,}
#pkts encaps: 22, #pkts encrypt: 22, #pkts digest: 22
#pkts decaps: 70, #pkts decrypt: 70, #pkts verify: 70
#pkts compressed: 0, #pkts decompressed: 0
#pkts not compressed: 0, #pkts compr. failed: 0
#pkts not decompressed: 0, #pkts decompress failed: 0
#send errors 0, #recv errors 0
local crypto endpt.: 40.22.1.1, remote crypto endpt.: 40.30.1.1
path mtu 1500, ip mtu 1500
current outbound spi: 0x631B0487(1662715015)
inbound esp sas:
spi: 0xB68D31FE(3062706686)
transform: esp-3des esp-sha-hmac ,
in use settings ={Tunnel, }
conn id: 2011, flow_id: VAM2+:11, crypto map: Virtual-Access2-head-0
sa timing: remaining key lifetime (k/sec): (4392206/10591)
IV size: 8 bytes
replay detection support: Y
Status: ACTIVE
inbound ah sas:
inbound pcp sas:
outbound esp sas:
spi: 0x631B0487(1662715015)
transform: esp-3des esp-sha-hmac ,
in use settings ={Tunnel, }
conn id: 2012, flow_id: VAM2+:12, crypto map: Virtual-Access2-head-0
sa timing: remaining key lifetime (k/sec): (4392214/10590)
IV size: 8 bytes
replay detection support: Y
Status: ACTIVE
outbound ah sas: