Setting up ESXi 5 iSCSI multipathing with jumbo frames can be confusing and complex. The process is much easier in vSphere 5 than it was in previous versions, and it’s no longer necessary to do the configuration from the command line. Here's a <a href="http://www.youtube.com/watch?v=Mu-HyD3E3cw">link</a> to an excellent instructional video that walks you through the entire process.