>I want to store nic addresses for example 00-A0-B7-34-F3-23.

You could create a CHECK constraint on the table as

CREATE TABLE foo (
...
NICAddr nchar(17) CHECK (NICAddr LIKE '[0-9A-F][0-9A-F]-[0-9A-F][0-9A-F]-[0-9A-F][0-9A-F]-[0-9A-F][0-9A-F]-[0-9A-F][0-9A-F]-[0-9A-F][0-9A-F]'),
... )

-Mike