Dual-Hop FCoE support is one of the main features of VC 4.01. This new feature allows the FCoE traffic to be propagated out of the enclosure to an external bridge which will handle the conversion of FCoE to FC traffic.

Dual-Hop FCoE solution has several advantages when compared to a traditional FC + Ethernet design.
With FCoE, the number of cables is reduced, this results in a simplification of the in-rack cable installation and consequently eliminates expensive equipment and reduces the overall solution cost. This feature is described as FCoE Dual Hop because there is two FCoE ‘hops’ between the server and the storage – the VC Module and the external FCoE ->FC bridge that connects the HP Virtual Connect modules to the storage. No additional external bridges are currently allowed in this configuration in order for Virtual Connect to guarantee the lossless of the FCoE connection.

HP put together a great cookbook on how to work with this new feature in VCM v4.01 and troubleshooting with upstream switches.
You can download the document here:
http://bizsupport1.austin.hp.com/bc/docs/support/SupportManual/c03808925/c03808925.pdf