Hint (GNU Radius Reference Manual)

ATTRIBUTE Hint 1040 string

Users: L-

Hints: -R

Huntgroups: -R

Additivity: Append

Proxy propagated: No

Use the Hint attribute to specify additional matching criteria depending on the hint (see Request Processing Hints — raddb/hints).

Let the hints file contain

DEFAULT Prefix = "S", Strip-User-Name = No
 Hint = "SLIP"

and the users file contain

DEFAULT Hint = "SLIP",
 NAS-IP-Address = 11.10.10.12,
 Auth-Type = System
 Service-Type = Framed-User,
 Framed-Protocol = SLIP

Then any user having a valid system account and coming from NAS ‘11.10.10.12’ will be provided SLIP service if his user name starts with ‘S’.