3Com 3C13618 Command Reference Manual page 659

It shall be noted that the subsequent authentication method is used only when the
authentication can not proceed normally instead of failing. Authentication unable to
proceed normally means that communication with the RADIUS server fails. Only
when the radius method is used will abnormality occur in authentication.
The five combination methods are listed as follows:
aaa authentication-scheme login default none
aaa authentication-scheme login default local
aaa authentication-scheme login default radius
aaa authentication-scheme login default radius none
aaa authentication-scheme login default radius local
Description
Using the aaa authentication-scheme login command, you can configure the AAA
login method list. Using the undo aaa authentication-scheme login command, you
can cancel the configured AAA login method list.
If it does not specify the authentication list for FTP and EXEC user, the authentication
method list defined by default will be adopted. The default authentication method is
local authentication.
In the AAA login authentication method list, three authentication methods can be
specified: local, radius and none. local is an authentication method via the local
database, radius is an authentication method via the RADIUS server, while none
indicates that no authentication is conducted.
The local database is configured via the local-user command.
As for non-default method lists, the undo aaa authentication-scheme login
command serves to cancel a method list; as for default method lists, it can restore the
default method to local authentication.
For related commands, see aaa authentication-scheme local-first, local-user
callback-number, local-user call-number, local-user ftp-directory, local-user
password, local-user service-type.
Example
# Configure the login default authentication method list with the following
requirements: use the RADIUS server for authentication first; if no acknowledgement
is received, then change to the local authentication.
[3Com]aaa authentication-scheme login default radius local
Security
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