Accessing the switch

TACACS+ offers the following advantages over RADIUS:

•TACACS+ uses TCP-based connection-oriented transport; whereas RADIUS is UDP based. TCP offers a connection-oriented transport, while UDP offers best-effort delivery. RADIUS requires additional programmable variables such as re-transmit attempts and time-outs to compensate for best-effort transport, but it lacks the level of built-in support that a TCP transport offers.

•TACACS+ offers full packet encryption whereas RADIUS offers password-only encryption in authentication requests.

•TACACS+ separates authentication, authorization, and accounting.

How TACACS+ authentication works

TACACS+ works much in the same way as RADIUS authentication.

1.Remote administrator connects to the switch and provides user name and password.

NOTE: The user name and password can have a maximum length of 128 characters. The password cannot be left blank.

2.Using Authentication/Authorization protocol, the switch sends request to authentication server.

3.Authentication server checks the request against the user ID database.

4.Using TACACS+ protocol, the authentication server instructs the switch to grant or deny administrative access.

During a session, if additional authorization checking is needed, the switch checks with a TACACS+ server to determine if the user is granted permission to use a particular command.

TACACS+ authentication features

Authentication is the action of determining the identity of a user, and is generally done when the user first attempts to log in to a device or gain access to its services. Switch software supports ASCII inbound login to the device. PAP, CHAP and ARAP login methods, TACACS+ change password requests, and one-time password authentication are not supported.

Authorization

Authorization is the action of determining a user’s privileges on the device, and usually takes place after authentication.

The default mapping between TACACS+ authorization privilege levels and switch management access levels is shown in the table below. The privilege levels listed in the following table must be defined on the TACACS+ server.

Table 4 Default TACACS+ privilege levels

User access levelTACACS+ level

 

 

user

0

 

 

oper

3

 

 

admin

6

 

 

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