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Example of Configuring VTY Authorization Based on Access Class Retrieved from the Line (Per Network Address)
Dell(conf)#ip access-list standard deny10
Dell(conf-ext-nacl)#permit 10.0.0.0/8
Dell(conf-ext-nacl)#deny any
Dell(conf)#
Dell(conf)#aaa authentication login tacacsmethod tacacs+
Dell(conf)#tacacs-server host 256.1.1.2 key Dell
Dell(conf)#
Dell(conf)#line vty 0 9
Dell(config-line-vty)#login authentication tacacsmethod
Dell(config-line-vty)#
Dell(config-line-vty)#access-class deny10
Dell(config-line-vty)#end
(same applies for radius and line authentication)
VTY MAC-SA Filter Support
Dell Networking OS supports MAC access lists which permit or deny users based on their source MAC address.
With this approach, you can implement a security policy based on the source MAC address.
To apply a MAC ACL on a VTY line, use the same access-class command as IP ACLs.
The following example shows how to deny incoming connections from subnet 10.0.0.0 without displaying a login prompt.
Example of Configuring VTY Authorization Based on MAC ACL for the Line (Per MAC Address)
Dell(conf)#mac access-list standard sourcemac
Dell(config-std-mac)#permit 00:00:5e:00:01:01
Dell(config-std-mac)#deny any
Dell(conf)#
Dell(conf)#line vty 0 9
Dell(config-line-vty)#access-class sourcemac
Dell(config-line-vty)#end
Two Factor Authentication (2FA)
Two factor authentication also known as 2FA, strengthens the login security by providing one time password (OTP) in addition
to username and password. 2FA supports RADIUS authentications with Console, Telnet, and SSHv2.
To perform 2FA, follow these steps:
● When the Network access server (NAS) prompts for the username and password, provide the inputs.
● If the credentials are valid:
○ RADIUS server sends a request to the SMS–OTP daemon to generate an OTP for the user.
○ A challenge authentication is sent from the RADIUS server as Reply–Message attribute.
○ If the Reply–Message attribute is not sent from the RADIUS server, the default text is the Response.
○ 2FA is successful only on providing the correct OTP.
● If the credentials are invalid, the authentication fails.
NOTE: 2FA does not support RADIUS authentications done with REST, Web UI, and OMI.
Handling Access-Challenge Message
To provide a two-step verification in addition to the username and password, NAS prompts for additional information. An
Access-Challenge request is sent from the RADIUS server to NAS.
The RADIUS server returns one of the following responses:
● Access-Challenge—If the user credentials are valid, the NAS server receives an Access-Challenge request from the
RADIUS server.
● Access-Accept—NAS validates the username and password. If the credentials are valid, the RADIUS server sends an
Access-Request to the short message service one time password (SMS-OTP) daemon to generate an OTP. The OTP is
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