Users Guide

254 Authentication, Authorization, and Accounting
error, the next method in the list is tried. This continues until all methods in
the list have been attempted. If no method can perform the service, then the
service fails. A method may return an error due to lack of network access,
misconfiguration of a server, and other reasons. If there is no error, the
method returns success if the user is allowed access to the service and failure
if the user is not.
AAA gives the user flexibility in configuration by allowing different method
lists to be assigned to different access lines. In this way, it is possible to
configure different security requirements for the serial console than for
Telnet, for example.
Methods
A method performs authentication or authorization for the configured
service. Not every method is available for every service. Some methods require
a username and password and other methods only require a password.
Table 9-1 summarizes the various methods:
Table 9-1. AAA Methods
Method Username? Password? Can Return an Error?
enable no yes yes
ias yes yes no
line no yes yes
local yes yes yes
none no no no
radius yes yes yes
tacacs yes yes yes