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HOWTO: Add Cisco FEX2K to Nexus 5K

As part of our recent enhancements, we’re looking to add a Cisco Fabric Extender (FEX2K) 2232TM unit to our existing Cisco Nexus 5548UP (N5K) units in Production.  FEX’s are essentially “external line cards” designed to add more ports to a Nexus 5K without trying to stuff them inside the same chassis.  The FEX itself has no ‘smarts’ and all configuration, intelligence, features and even switching, comes by nature of the backplane/supervisor on the N5K.  This HOWTO will cover that basic hardware addition.

The following assumptions are made:

  • You have a Nexus 5548UP (N5K) switch
  • You have a FEX 2232TM (FEX2K) fabric extender
  • You have used the N5K Ports 0/1 to connect to the FEX2K’s Ports 33/34
  • The N5K is running NX-OS v7.x

Not in scope:

  • Anything related to port or switch configurations in general.  We are ONLY reviewing addition of the FEX2K to the N2K to add ports at this time.

1) Login to the Nexus 5K switch, and enter Configuration mode (conf t)

2) Add the FEX feature with the command “feature fex”:

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3) Run “show fex” to see the currently attached FEX units:

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4) Because we’re using the N5K Port 1 and 2 to attach the FEX for 2x10GbE links, we need to create a port-channel:

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I’d recommend numbering the channel-group the same as your FEX ID. 

You’ll note by the end, that we don’t have to do any configuration on the FEX itself to let it know it’s part of this Nexus 5K.  Essentially the 5K grabs it and assumes it will have full use of the unit.

5) Next, we’ll configure the port-channel:

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The common switchport modes are “access” and “trunk”.  The FEX adds a “fex-fabric”, specific to adding a fabric extender.

6) If all goes well, you can run a “show fex” to see the FEX:

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And it should show “Image Download” as it downloads the OS code to the unit automatically. 

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You can run “show fex detail” to see additional detail.  Note that “FEX version” is v5.2 and the Switch Version is v7.0 above.

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When the upgrade is complete, you can run “show fex” again to see the state of “Online”.  Note that there’s no indication when it’s done, so just check periodically.

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Also a “show fex detail” will allow you to confirm the FEX and SWITCH versions now match.

7) Create a FEX entry:

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8) Check your interfaces:

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You can see that the ports are called “Eth101/1/1-32”.  The 101 is your FEX ID from above.

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And a “show interface status” will show everything.  While I’ve summarized it, you can see how the Nexus 5548UP ports are referred to as “Eth1/1-32”

To configure a 10/100/1000/10000 switch port on the FEX2K then, you would enter “int Eth101/1/9” to configure port 9.

At this point you now have a functioning FEX2K “line card” added to your Nexus N5K.  Advanced configuration such as VLAN’s, and other switch requirements are not in scope with this document.  As the FEX simply adds additional ports, anything you would have normally done is now possible, with the extra ports.

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Categories: Cisco, FEX2K, Hardware, N5K, Nexus
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