Cisco TrustSec Switch Configuration Guide

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Updated:
May 18, 2015

Chapter: Configuring Endpoint Admission Control

Configuring Endpoint Admission Control

Revised: May 28, 2010

This chapter contains the following sections:

Information About Endpoint Admission Control

In TrustSec networks, packets are filtered at the egress, not the ingress to the network. In TrustSec endpoint authentication, a host accessing the TrustSec domain (endpoint IP address) is associated with a Security Group Tag (SGT) at the access device through DHCP snooping and IP device tracking. The access device transmits that association (binding) through SXP-to-TrustSec hardware-capable egress devices, which maintain a continually updated table of Source IP to SGT bindings. Packets are filtered on egress by the TrustSec hardware-capable devices by applying security group ACLS (SGACLs).

Endpoint Admission Control (EAC) access methods for authentication and authorization can include the following:

  • 802.1X port-based Authentication
  • MAC Authentication Bypass (MAB)
  • Web Authentication (WebAuth)

All port-based authentication can be enabled with the authentication command. Each access method must be configured individually per port. The flexible authentication sequence and failover features permit the administrator to specify the failover and fallback sequence when multiple authentication modes are configured and the active method fails. The 802.1X host mode determines how many endpoint hosts can be attached per 802.1X port.

Basic EAC Configuration Sequence

1.blank.gif Configure the Cisco Secure ACS to provision SGTs to authenticated endpoint hosts.

2.blank.gif Enable SXP on access switches. See the chapter, “Configuring SGT Exchange Protocol.”

3.blank.gif Enable any combination of 802.1X, MAB, or WebAuth authentication methods on the access switch.

4.blank.gif Enable DHCP and IP device tracking on access switches.

802.1X Authentication Configuration

The following example shows the basic 802.1x configuration on a Gigabit Ethernet port:

Switch(config)# dot1x system-auth-control
Switch(config)# interface GigabitEthernet2/1
Switch(config-if)# authentication port-control auto
Switch(config-if)# dot1x pae authenticator

Verifying the 802.1X Configuration

To verify 802.1X authentication configuration, use the show authentication interface command.

Switch# show authentication interface gigabitEthernet 2/1
*May 7 11:22:06: %SYS-5-CONFIG_I: Configured from console by console
 
Client list:
Interface MAC Address Domain Status Session ID
Gi2/1 000c.293a.048e DATA Authz Success AC1AD01F0000000904BBECD8
 
Available methods list:
Handle Priority Name
3 0 dot1x
Runnable methods list:
Handle Priority Name
3 1 dot1x
 

And to verify the port has successfully authenticated:

Switch# show dot1x interface gigabitEthernet 2/1 details
 
Dot1x Info for GigabitEthernet2/1
-----------------------------------
PAE = AUTHENTICATOR
PortControl = AUTO
ControlDirection = Both
HostMode = SINGLE_HOST
QuietPeriod = 60
ServerTimeout = 30
SuppTimeout = 30
ReAuthMax = 2
MaxReq = 2
TxPeriod = 30
 
Dot1x Authenticator Client List
-------------------------------
Supplicant = 000c.293a.048e
Session ID = AC1AD01F0000000904BBECD8
Auth SM State = AUTHENTICATED
Auth BEND SM State = IDLE
Port Status = AUTHORIZED

MAC Authentication Bypass Configuration

MAC Authentication Bypass (MAB) enables hosts or clients that are not 802.1X capable to join 802.1X-enabled networks. It is not required to enable 802.1X authentication prior to enabling MAB.

The following example is a basic MAB configuration on a Catalyst switch:

switch(config)# interface GigabitEthernet2/1
switch(config-if)# authentication port-control auto
switch(config-if)# mab
 

For additional information on configuring MAB authentication, see the configuration guide for your access switch.

Verifying the MAB Configuration

To verify the MAC Authentication Bypass configuration, use the show authentication interface command.

switch# show authentication interface gigabitEthernet 2/1
 
Client list:
Interface MAC Address Domain Status Session ID
Gi2/1 000c.293a.048e DATA Authz Success AC1AD01F0000000A04CD41AC
 
Available methods list:
Handle Priority Name
2 1 mab
Runnable methods list:
Handle Priority Name
2 0 mab

 

To verify that the port has successfully authenticated, use the show mab interface command.

switch# show mab interface gigabitEthernet 2/1 details
MAB details for GigabitEthernet2/1
-------------------------------------
Mac-Auth-Bypass = Enabled
 
MAB Client List
---------------
Client MAC = 000c.293a.048e
Session ID = AC1AD01F0000000A04CD41AC
MAB SM state = ACQUIRING
Auth Status = UNAUTHORIZED

Web Authentication Proxy Configuration

Web Authentication Proxy (WebAuth) allows the user to use a web browser to transmit their login credentials to the Cisco Secure ACS though a Cisco IOS web server on the access device. WebAuth can be enabled independently. It does not require 802.1X or MAB to be configured.

The following example shows a basic WebAuth configuration on a Gigabit Ethernet port:

switch(config)# ip http server
switch(config)# ip access-list extended POLICY
switch(config-ext-nacl)# permit udp any any eq bootps
switch(config-ext-nacl)# permit udp any any eq domain
switch(config)# ip admission name HTTP proxy http
switch(config)# fallback profile FALLBACK_PROFILE
switch(config-fallback-profile)# ip access-group POLICY in
switch(config-fallback-profile)# ip admission HTTP
switch(config)# interface GigabitEthernet2/1
switch(config-if)# authentication port-control auto
switch(config-if)# authentication fallback FALLBACK_PROFILE6500(config-if)#ip access-group POLICY in

Verifying Web Authentication Proxy Configuration

To verify the Web Authentication Proxy configuration, access the interface IP address with a web browser. If configured correctly, the access device generates a challenge and accepts valid login information.

To verify the Web Authentication proxy configuration with the CLI, use the show authentication interface command.

switch# show authentication interface gigabitEthernet 2/1
 
Client list:
Interface MAC Address Domain Status Session ID
Gi2/1 000c.293a.048e DATA Authz Success AC1AD01F0000000904BBECD8
 
Available methods list:
Handle Priority Name
1 2 webauth
Runnable methods list:
Handle Priority Name
1 0 webauth

Flexible Authentication Sequence and Failover Configuration

Flexible Authentication Sequence (FAS) allows the access port to be configured for 802.1X, MAB, and WebAuth authentication methods, specifying the fallback sequence if one or more of the authentication methods are not available. The default failover sequence is as follows:

  • 802.1X port-based Authentication
  • MAC Authentication Bypass
  • Web Authentication

Layer 2 authentications always occur before Layer 3 authentications. That is, 802.1X and MAB must occur before WebAuth.

The following example specifies the authentication sequence as MAB, dot1X, and then WebAuth.

switch(config)# interface gigabitEthernet 2/1
switch(config-if)# authentication order mab dot1x webauth
switch(config-if)^Z
 

For additional information on FAS, see the Cisco document, Flexible Authentication Order, Priority, and Failed Authentication at the following URL:

http://www.ciscosystems.com.pe/en/US/prod/collateral/iosswrel/ps6537/ps6586/ps6638/application_note_c27-573287_ps6638_Products_White_Paper.html

802.1X Host Modes

Four host classification modes can be configured per port:

  • Single Host —Interface-based session with one MAC address
  • Multi Host—Interface-based session with multiple MAC addresses per port
  • Multi Domain—MAC + Domain (VLAN) session
  • Multi Auth—MAC-based session with multiple MAC address per port

Pre-Authentication Open Access

The Pre-Authentication Open Access feature allows clients and devices to gain network access before port authentication is performed. This process is primarily required for the PXE boot scenario, where a device needs to access the network before PXE times out and download a bootable image that may contain a supplicant.

DHCP Snooping and SGT Assignment

After the authentication process, authorization of the device occurs (for example, dynamic VLAN assignment, ACL programming, etc.). For TrustSec networks, a Security Group Tag (SGT) is assigned per the user configuration in the Cisco ACS. The SGT is bound to traffic sent from that endpoint through DHCP snooping and the IP device tracking infrastructure.

The following example enables DHCP snooping and IP device tracking on an access switch:

switch# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
switch(config)# ip dhcp snooping
switch(config)# ip dhcp snooping vlan 10
switch(config)# no ip dhcp snooping information option
switch(config)# ip device tracking

Verifying the SGT to Endpoint Host Binding

To verify that hosts are visible to DHCP Snooping and IP Device Tracking, use the show ip dhcp snooping binding and show ip device tracking commands.

switch# show ip dhcp snooping binding
 
MacAddress IpAddress Lease(sec) Type VLAN Interface
------------------ --------------- ---------- ------------- ---- --------------------
00:0C:29:3A:04:8E 10.252.10.10 84814 dhcp-snooping 10 GigabitEthernet2/1
Total number of bindings: 1
 
 
switch# show ip device tracking all
 
IP Device Tracking = Enabled
IP Device Tracking Probe Count = 3
IP Device Tracking Probe Interval = 30
--------------------------------------------------------------
IP Address MAC Address Interface STATE
--------------------------------------------------------------
10.252.10.10 000c.293a.048e GigabitEthernet2/1 ACTIVE

 

To verify that the correct SGT is bound to an endpoint IP address, use the show cts role-based sgt-map command.

switch# show cts role-based sgt-map all
 
Active IP-SGT Bindings Information
IP Address SGT Source
============================================
1.1.1.1 7 INTERNAL
10.252.10.1 7 INTERNAL
10.252.10.10 3 LOCAL
10.252.100.1 7 INTERNAL
172.26.208.31 7 INTERNAL
 
IP-SGT Active Bindings Summary
============================================
Total number of LOCAL bindings = 1
Total number of INTERNAL bindings = 4
Total number of active bindings = 5

Cisco TrustSec Endpoint Access Control Feature Histories

For a list of supported platforms, supported features, and the minimum required IOS releases, see
the Cisco TrustSec Platform Support Matrix at the following URL:

http://www.cisco.com/en/US/solutions/ns170/ns896/ns1051/trustsec_matrix.html

Otherwise, see product release notes for detailed feature introduction information.

 

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