FCoE is possible between two Data Centres by using VE ports to build multi-hop FCoE fabrics that interconnecting FCF, the VE port functions as a FC E-port on top of a lossless ethernet fabric.
The maximum distance between two Cisco Nexus 5000 Series switches is 3000m for FCoE (lossless Ethernet) traffic with NX-OS 5.0(2)N1.1. It can be enabled using the pause no-drop buffer-size buffer-size pause-thresholdxoff-size resume-threshold xon-size command in QOS configuration. Here are the maximum distances:
Nexus 55xx to Nexus 55xx – 3km
Nexus 50×0 to Nexus 50×0 – 3km
Nexus 50×0 to Nexus 55xx – 3km
Nexus 55xx to Nexus 2232 – 300m
Nexus 50×0 to Nexus 2232 – 300m