accomplish the task is to install and configure the Cisco DUO Authentication Proxy and configure the identity source sequence within Cisco ISE. This will allow the engineer to integrate Cisco ISE with Cisco DUO for TACACS+ device administration using Active Directory as the primary authentication source and Cisco DUO as the secondary authentication source for multi-factor authentication (MFA). The steps to configure this solution are as follows12:
Install and configure the Cisco DUO Authentication Proxy on a Windows or Linux machine. The proxy will act as a RADIUS server that communicates with Cisco ISE and a RADIUS client that communicates with Cisco DUO cloud. The proxy will also connect to Active Directory for the primary authentication of the users.
Configure the proxy by editing the authproxy.cfg file. The file should include the following sections:
[ad_client]: This section defines the connection parameters to Active Directory, such as the host, service_account_username, service_account_password, and search_dn.
[radius_server_auto]: This section defines the RADIUS server parameters for the proxy, such as the ikey, skey, api_host, radius_ip_1, radius_secret_1, and client parameters. The ikey, skey, and api_host are obtained from the Cisco DUO web portal when creating a RADIUS application. The radius_ip_1 and radius_secret_1 are the IP address and shared secret of the Cisco ISE node that will send authentication requests to the proxy. The client parameter specifies the authentication method for Cisco DUO, such as auto, push, phone, or passcode.
[main]: This section defines the global settings for the proxy, such as the debug, log_max_size, and log_max_files parameters.
Restart the proxy service after saving the authproxy.cfg file.
Configure Cisco ISE as a TACACS+ server and add the proxy as an external RADIUS server. The steps are as follows:
Navigate to Administration > System > Deployment and enable the Device Administration Service on the appropriate node.
Navigate to Work Centers > Device Administration > Network Resources and add the network devices that will use TACACS+ for device administration. Specify the device name, IP address, device type, and shared secret.
Navigate to Work Centers > Device Administration > Network Access and add the proxy as an external RADIUS server. Specify the server name, IP address, port, shared secret, and timeout. Optionally, enable the Continue for additional authorization policy option to allow Cisco ISE to perform authorization based on the user’s Active Directory attributes after successful authentication by Cisco DUO.
Navigate to Work Centers > Device Administration > Policy Elements > Results > TACACS Profiles and create a TACACS profile for device administration. Specify the profile name, type, and custom attributes, such as the shell:roles and shell:priv-lvl attributes.
Navigate to Work Centers > Device Administration > Policy Sets and create a policy set for device administration. Specify the policy set name, conditions, and results. The conditions can be based on the device type, the protocol, or the identity source sequence. The results can be the TACACS profile and the external RADIUS server (the proxy).
Configure the network devices to use TACACS+ for device administration and specify Cisco ISE as the TACACS+ server and the proxy as the RADIUS server. The configuration commands may vary depending on the device type and model, but the general syntax is as follows:
aaa new-model
aaa authentication login default group tacacs+ local
aaa authorization exec default group tacacs+ local
aaa accounting exec default start-stop group tacacs+
tacacs server ISE
address ipv4
key
radius server DUO
address ipv4 auth-port
key
Test the solution by logging into the network devices using Active Directory credentials. The user should receive a Cisco DUO prompt for the second factor authentication, such as a push notification, a phone call, or a passcode. After approving the second factor authentication, the user should be granted access to the device with the appropriate privileges based on the TACACS profile and the Active Directory attributes.
References := 1: Duo MFA Integration with ISE for TACACS+ Device Administration with Microsoft Active Directory Users - Cisco Community 2: Protecting Access to Network devices with ISE TACACS+ and DUO MFA - Cisco Community
