When the configuration for the network-qos policy-map sets the class-default to jumbo MTU, the show queuing interface command indicates that the MTU for class-default is 1500.
An incorrect startup configuration may exist after an upgrade.
If the switch has been upgraded to the 4.2(1)N1(1) release, make sure that you have used the write erase command to delete the startup configuration. You can save the configuration first to another file name.
After the Nexus 5000 switch boots up with an empty configuration, reapply the original configuration. You might lose your connectivity to the Nexus 5000 if you are using Telnet or SSH. It is recommended that you use the console for this procedure.