Arista switches use the following attribute values:
- Arista Vendor number: 30065
- Attribute: Arista-AVPair 1 string
Acceptable string values for Arista-AVPair include:
- shell:priv-lvl=(privilege level of a user, 0-15)
- shell:roles=(list of roles for a user)
For more information refer to Arista Documentation
The NPS Example would look like this.

Basic Config
Radius config to allow only the use of radius with local as a backup when radius is down. authentication flow -> radius -> local
radius-server key radius-password
radius-server host 10.10.8.4
!
aaa authentication login default group radius local
aaa authorization exec default group radius local
!
Radius config to allow the use of radius or local. authentication flow -> local -> radius
radius-server key 7 070C285F4D06
radius-server host 10.10.8.4
!
aaa authentication login default local group radius
aaa authorization exec default local group radius
!