On a Nexus, use a route-map command with a set clause of metric-type type-[½] in order to have the same functionality as in IOS using the default-information originate always metric-type [½] command.
For example :
* switch(config)#route-map STAT-OSPF, permit, sequence 10
* switch(config-route-map)#match interface ethernet 1/2
* switch(config-route-map)#set metric-type {external | internal | type-1 | type-2}
