ISE - AAA radius authentication for NAD access

Question

Hi ,
I have configured the switches to use the ISE as the Radius server to authenticate with , on the ISE i've configured an authentication policy
for the "NADs" using the "Wired Devices" group which points to the AD indentity source to authenticate against .
While testing the login access to the switches we've come up with 2 results :
1.A domain user can indeed login to the switch as intended.
2.Every domain user which exists in the AD indentity source can login , this is an undesired result .
So I am trying to search for a way to restrict access to the NADs to only a particular group belonging to the AD , for example the group/ou
of the IT_department only .
I haven't been successfull , would appreciate any ideas on how to accomplish this .
Switch configurations :
=================
aaa new-model
aaa authentication login default group radius local
ISE Authentication policy
==================
Policy Name : NADs Authentication
Condition:  "DEVICE:Device Type Equals :All Device Types#Wired"
Allowed Protocol : Default Network Access
use identity source : AD1

Answer 1

Thank you for the quick replys , and now  ok , I've configured the following authorization policy :
Rule Name : Nad Auth
Conditions
if: Any
AND : AD1:ExternalGroups EQUALS IT_Departments
Permissions , then PermitAccess
What I don't understand is that it needs to match an "identity group" which can be either "Endpoint Identity group" or "Users Identity group" , I am limited with the if statement and cannot chose the same device group a choose before .
How can i do that , i am thinking ahead an asking myself if in other cases a user might match this policy rule and can interfer ?