What is Cisco Nexus? The Cisco Nexus series switches are modular and fixed port network switches designed for the data center. What is difference between Cisco switch and Nexus switch? Cisco catalyst switches are mainly designed for distro/core layers in campus network vs the Nexus is mainly for data centers. Nexus series switches can support Ethernet, Fiber Channel and FCOE all in the same chassis but the catalyst don't. The catalyst switches support only Ethernet.