Specifies that the request must come from a Client with the
specified NasType. You can use an exact, alternation or regular expression
match.
<Client xxx>
NasType Livingston
....
</Client>
<Client yyy>
NasType Ascend
....
</Client>
# This is can only log in through xxx, since it has a NasType
# of Livingston
username Password=fred,NasType=Livingston