Terminal Access Controller Access-Control System Plus (TACACS+) protocol provides better Authentication security than RADIUS because it encrypts usernames and passwords (instead of just passwords), and is also more reliable (it uses TCP instead of UDP).
When you predefine dynamic administrator roles on the server, use lower-case to specify the role (for example, enter superuser, not SuperUser)..
When authenticating to the TACACS+ server, the firewall first tries Challenge-Handshake Authentication Protocol (CHAP) and falls back to Password Authentication Protocol (PAP) if the server rejects the CHAP request. This will happen if, for example, the server doesn’t support CHAP or isn’t configured for CHAP. CHAP is the preferred protocol because it is more secure than PAP. After falling back to PAP for a particular TACACS+ server, the firewall uses only PAP in subsequent attempts to authenticate to that server. The firewall records a fall back to PAP as a medium severity event in the System logs. If you modify any fields in the TACACS+ server profile and then commit the changes, the firewall reverts to first trying CHAP for that server.
Configure a TACACS+ Server Profile
Add a TACACS+ server profile. Select Device > Server Profiles > TACACS+ and click Add. Enter a Profile Name to identify the server profile. For a firewall with more than one virtual system (vsys), select the Location (vsys or Shared) where the profile is available. For the Timeout, enter an interval in seconds after which an authentication request times out (range is 1-20, default is 3). Select the Use single connection for all authentication check box to use the same TCP session for all authentications that use this profile. This option improves performance by avoiding the need to start and end a separate TCP session for each authentication. The check box is cleared by default. For each TACACS+ server, click Add and enter a Name (to identify the server), server IP address or FQDN ( TACACS+ Server field), Secret / Confirm Secret (a key to encrypt usernames and passwords), and server Port for authentication requests (default is 49). If you use an FQDN address object to identify the server and you subsequently change the address, you must commit the change for the new server address to take effect. Click OK.
Implement the TACACS+ server profile. Assign the TACACS+ server profile to an authentication profile or sequence. Test a TACACS+ Authentication Profile to verify that the firewall or Panorama can connect to the TACACS+ server. Assign the authentication profile or sequence to an administrator account or to a firewall service for end users. Commit your changes.

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