This read-only value indicates whether this interface's management-only role can be reconfigured by an admin: non-configurable, configurable, or fixed. It tells management tools whether attempting to set the interface's role to management-only on this particular port is even possible, since some interfaces have a hard-wired role. A value of fixed on a given NIC means the array locks that port's role and any attempt to change it via the role object will be rejected.