Most of the time Nexus 3K used for Low Latency for cut through the traffic, but some use case required to QoS appl.
bare in mind all the device not support this, since we are not sure what is the model you have.
Not sure why you buy 10GB port to limit to MB speed, Business wise not make any sense here.
below config - test and advise.
config t
policy-map type qos 2mbps-limit
class class-default
police cir percent 1 bc 200 ms conform transmit violate drop
interface Ethernet1/1-3
service -policy in 2mbps-limit
end
reference :
https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus3000/sw/qos/602_U1_1/b_3k_QoS_Config_602_U11/b_3k_QoS_Config_602_U11_chapter_0100.html
