Known CNA cards that require active SFP+ cable assemblies include: Brocade (1010/1020 CNA) and QLogic. The EMC VNX Series nified Storage Systems also requires active SFP+ Passive DAC assemblies. If using SFP+ DAC cable assemblies between equipment that should be open, and the link is not working, a quick check can be performed by plugging in a different SFP+ cable assembly between the same two ports. If the link does come up, it is likely a problem with the first SFP+ Passive DAC assembly. Another key benefit of 10GBASE-T is backward compatibility. Using the standard RJ45 connector, 10GBASE-T ports can connect to 1 Gigabit and even 100 Megabit interfaces, allowing end-users to transparently upgrade to 10GE from their Fast Ethernet/Gigabit Ethernet networks. The ability to auto-negotiate between 1G and 10G speeds allows users to determine which links will be high speed and low speed, and switch between the two without a hardware upgrade. In comparison, 10GBASE-SFP+ Passive DAC products typically have limited or no backward compatibility with previous speeds. An acquisition cost comparison analysis for data center use of 10GBASE-T versus SFP+ DAC cabling shows that 10GBASE-T provides 50% cost reduction over SFP+ Passive DAC. A corresponding cost reduction in equipment maintenance and on-going operations is expected.