Configure Fabric Extender to Nexus 5k via Port-Channel

First, let’s just enjoy this moment.. This is my first Cisco-centered blog…. EVER!

Ok, now that we’re done with that collective “WHAT?!!”, let’s get to business!

Cisco has a pretty neat technology called Fabric Extenders. If you follow my blog, then you’re probably a Juniper gear-head, so think of it as EX virtual-chassis’ using the 10G revenue ports. The Nexus FEX (Fabric Extender) switch is essentially a “line card” or “switch card” for the system as a whole. It’s an AWESOME way to extend one switch throughout the data center.

Why extend a switch with fabric extenders?

  1. Eliminate the Spanning Tree Protocol (STP).
    • If you’ve ever troubleshot or designed a layer 2 network, you know all about spanning tree and the pain it can bring network engineers.
    • Each switch vendor has it’s own way to remove the need for STP and each vendor has benefits over the others.  The main benefit they all share is this: A switch fabric/extender failure fails over faster than RSTP (rapid spanning tree protocol) could ever failover.  Faster failover means happier customers and executives.
  2. Reduce operational headaches.
    • Have you ever logged into a data center switch only to realize it’s switch-xyz-002 instead of switch-xyz-001.  Having to document the interconnections and manage the control plane of multiple switches is “soooo last decade”.  Why not just log into one switch and control the whole data center switching environment?

How to configure a Nexus 2232 as a Fabric Extender Associate with a Port Channel connected to a Nexus 5000:

All configuration is done on the Nexus 5000.  No configuration is needed for the Nexus 2000.

  1. Add the “feature” to the Nexus
  2. Provision the “slot” it will use
  3. Provision the FEX Switch
  4. Provision the Port Channel
  5. Provision the FEX Associate Ports and make sure they’re configured for the correct Port Channel
  6. Provision the FEX switch ports as you would normal switch ports

The end configuration should look something like the following:



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Responses to “Configure Fabric Extender to Nexus 5k via Port-Channel”

  1. So, when I get to step 6, the interface I use doesn’t have the switchport mode option. Only host and monitor.
    Other ethernet ports have the mode switch available.

    School-9-Switch(config)# interface ethernet 1/32
    School-9-Switch(config-if)# switchport ?
    host Set port host
    monitor Monitor session related traffic

    This system is running
    BIOS: version 3.6.0
    loader: version N/A
    kickstart: version 5.2(1)N1(1)
    system: version 5.2(1)N1(1)

    • Did you set the 2Ks as associates? That seems to be the key…

      fex 100
      hardware N2248T queue-limit 327680
      pinning max-links 1
      description “[-[METASWITCH]-]”
      serial FOX1728GPAR
      type N2248T

      interface Ethernet1/15
      switchport mode fex-fabric
      fex associate 150
      channel-group 20