My Cisco Nexus Study Notes

  • The vPC technology is configured between two and only two Nexus switches. Catalyst switches provide no vPC functionality. The switches bound together in the vPC setting are called vPC peer switches.
  • Unlike other stacking technologies like VSS, Nexus switches in a vPC configuration do not form a single control plane; they maintain their own control plane, and share a common control plane between them. That is why we can ssh into each Nexus switch seperately, while that is not possible in a VSS setup.
  • vPC peer switches are linked together using at least 2*10Gbps links, configured in a port-channel. These links form what is called the vPC peer link.
  • vPC peer switches maintain also what is called a vPC keepalive link. This is NOT a physical link, but rather a logical link that runs across the vPC peer link.
  • Nexus switches in a vPC setup must be configured with something called a vPC domain. two vPC peer switches must have the same vPC domain value.
  • vPC peer switches are taken from this list of product family:
    • Nexus 5000, aka N5k
    • Nexus 7000, aka N7k
    • Nexus 9000, aka N9k
  • vPC peer switches – which are either Nexus 5000, Nexus 7000 or Nexus 9000 – are not intended to be physically directly connected to end hosts such as servers. They must be equipped with a special kind of connections to Nexus 2000 series switches, or simply N2k. For that matter we call:
    • the N5k, N7k or N9k as parent switches
    • the N2k as Fabric EXtenders (aka FEX).
  • So the Nexus 2000 are our FEXes. And the connection between the FEX and the parent switches are called FEX links.
  • Servers will then connect to the Nexus 2000 series.
  • Important to notice: given two servers A and B physically connected to a same Nexus 2000 series: when A communicates with B, packets do NOT flow directly from port A to port B, but rather upstream to the parent switch then downstream again to port B. That is because the FEXes do not have their own data plane.
  • There are different product families for the Nexus 2000. Some of them support only 1Gbps access port bandwidth, and others support up to 10Gbps copper and fiber. In any way, all Nexus 2000 models have dedicated uplink ports for the FEX links. But when you choose a Nexus 2000 series switch, you must make sure that it supports the parent switch model that you already have in your network, or intent to purchase. Why? because not all Nexus 2000 series support Nexus 5000, Nexus 7000 or Nexus 9000!

I leaned this stuff from the following courses which I recommand to you:

  • Pluralsight, Cisco CCNA Data Center: Nexus, Advanced Switching & SAN

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