HP Cisco Nexus 5000 Cisco Nexus 5000 Series Switch CLI Software Configuration - Page 268

Information About TACACS+ Chapter 18 Configuring TACACS+ Send feedback to [email protected] • TACACS+ Server Monitoring, page 18-3 TACACS+ Advantages TACACS+ has the following advantages over RADIUS authentication: • Provides independent AAA facilities. For example, the Nexus 5000 Series switch can authorize access without authenticating. • Uses the TCP transport protocol to send data between the AAA client and server, making reliable transfers with a connection-oriented protocol. • Encrypts the entire protocol payload between the switch and the AAA server to ensure higher data confidentiality. The RADIUS protocol only encrypts passwords. User Login with TACACS+ When a user attempts a Password Authentication Protocol (PAP) login to a Nexus 5000 Series switch using TACACS+, the following actions occur: 1. When the Nexus 5000 Series switch establishes a connection, it contacts the TACACS+ daemon to obtain the username and password. Note TACACS+ allows an arbitrary conversation between the daemon and the user until the daemon receives enough information to authenticate the user. This action is usually done by prompting for a username and password combination, but may include prompts for other items, such as the user's mother's maiden name. 2. The Nexus 5000 Series switch will receive one of the following responses from the TACACS+ daemon: • ACCEPT-User authentication succeeds and service begins. If the Nexus 5000 Series switch requires user authorization, authorization begins. • REJECT-User authentication failed. The TACACS+ daemon either denies further access to the user or prompts the user to retry the login sequence. • ERROR-An error occurred at some time during authentication dither at the daemon or in the network connection between the daemon and the Nexus 5000 Series switch. If the Nexus 5000 Series switch receives an ERROR response, the Nexus 5000 Series switch tries to use an alternative method for authenticating the user. The user also undergoes an additional authorization phase, if authorization has been enabled on the Nexus 5000 Series switch. Users must first successfully complete TACACS+ authentication before proceeding to TACACS+ authorization. 3. If TACACS+ authorization is required, the Nexus 5000 Series switch again contacts the TACACS+ daemon and it returns an ACCEPT or REJECT authorization response. An ACCEPT response contains attributes that are used to direct the EXEC or NETWORK session for that user and determines the services that the user can access. Services include the following: • Telnet, rlogin, Point-to-Point Protocol (PPP), Serial Line Internet Protocol (SLIP), or EXEC services 18-2 Cisco Nexus 5000 Series Switch CLI Software Configuration Guide OL-16597-01