Some NX-OS features can’t be manually enabled

The whole idea around features in NX-OS has been intriguing to me. It’s a good idea – I like it. It seems very similar to services on many other OSs (particularly *nix systems), however it doesn’t always strike me as having a rich feature set as of now.

For instance, the NX-OS config guides repeatedly refer to the show feature command to look at which features are enabled.  I’ve already mentioned that this command doesn’t exist today in older NX-OS versions – the currently-available NX-OS versions today support this feature (a reader confirmed this on the N7k and I’ve confirmed it on the N5k).  See this article for more info.  There are some interesting behaviors around features, in that some are manually enabled, while others are automatically enabled and disabled as needed.  Let’s dig into this a little deeper for an example…

It looks like some features can’t be manually controlled. Take a look at the FEX feature.

N5K(config)# show run | i feature
feature fcoe
N5K(config)#
N5K(config)# feature fex
ERROR: Configuration not allowed
N5K(config)#

Now let’s turn up an FEX:

N5K(config)# fex 100
N5K(config-fex)# do sh run | i feature
feature fcoe
feature fex
N5K(config-fex)#

That’s literally it! I can’t turn it on or off:

N5K(config-fex)# exit
N5K(config)# no feature fex
ERROR: Configuration not allowed
N5K(config)#

But it obviously works. I just thought that this was interesting as I was under the impression that any features that were shown in the config were under the direct control of the device administrator. This isn’t the case. I wonder what other features exist, but don’t show up until something is configured? It’s almost like an easter egg hunt… I like surprises (good ones, anyway), so I’ll be keeping my eyes open for what other features I find!

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