ant to the 5000 and is not shared outside the connected 5000. If you connect one FEX to two 5Ks, they can be named differently, SO be careful because this will be very confusing: NX-5K-1 (config)# fex ? <100-199> FEX number Here is a config snippet from a configured FEX: fex 100 description FEX0100 type "Nexus 2148T" The description in this case was added automatically by the switch and can be changed. The type was also added by the switch upon discovery of the FEX and cannot be changed. Physical connection When connecting a port or ports on the 5K to the FEXs fabric ports, you must configure the 5K's ports as fabric ports using the switchport mode fex-fabric command. You must then assign the ports to the FEX using the fex associate fex-number command. When more than one uplink is used, the ports can be bonded into an EtherChannel: interface Ethernet 1/1 switchport mode fex-fabric fex associate 100 channel-group 10 Chapter 18: Cisco Nexus The FEX associate command is what designates this FEX as FEX 100 within the switch. When a FEX is first recognized, it will likely need to download the proper microcode from the 5000 or 7000 to which it is connected. This process can take 10-15 minutes and will involve the FEX restarting. There may be no indication of this happening, SO either go get some lunch or obsessively reenter the show fex command to see what's going on. You could do both, but make sure you don't leave any crumbs in the data center. Pinning Normally, with a 48-port 1 Gbps switch, assuming a 4x10 Gbps uplink EtherChannel totaling 40 Gbps, the uplink will have a possible oversubscription ratio of 4.8:1. Pinning allows us to assign banks of ports to individual uplinks instead of having all the ports share a single EtherChannel. Why would we do this? Read on. Why is the ratio 4.8:1 and not 1.2:1? After all, there is a 40 Gbps uplink and forty-eight 1 Gbps ports. The discrepancy is due to the nature of EtherChannel load balancing. Remember, an EtherChannel is not really a faster link, but rather multiple same-