Avoiding human errors with Cisco NX-OS "Grace Periods"

Looking out to Guishan Island (the left top far)
Taken around Northeast Coast National Scenic Area (東北角海岸國家風景區), Yilan County, Taiwan.

Cisco offers “Evaluation” time intervals (Grace Periods) for some features of Cisco NX-OS on Data Center switches such as Nexus 7000 or Nexus 5000. It is a nice design because customer can evaluate whether those specific features are suitable for their needs or not, before they really buy that license. This is also very useful for PoC (Proof of Concept) installation.

It is really simple to start evaluation. First we enable evaluation grace periods by “license grace-period” command. Then we only have to type “feature X” commands at the CLI as if we have bought the license.

Of course, the terminal would print out some warning messages like this:

NOTICE: NX-OS LICENSED FEATURES NEED ATTENTION

-----------------------------------------------------------------------------
Feature                      Ins  Lic   Status Expiry Date Comments
                                 Count
-----------------------------------------------------------------------------
LAN_ENTERPRISE_SERVICES_PKG   No    -   In use             Grace 14D 6H
-----------------------------------------------------------------------------
**** WARNING: License(s) about to expire. When license(s) expire,
all licensed conditional features will be disabled ****

The 120 days (almost 4 months) is indeed a long time. It is very enough for any serious evaluations. The customer only has to buy and install the license file before the evaluation expires. The whole buy-and-install process would not cause any service outage. However, when the evaluation grace period expires, that feature would simply stop working by itself.

In this way, it creates some room for possible human error. Suppose if we did not notice we have enabled some evaluation license and they are indeed in use, we might also forget to install the required license files because everything would be running just fine.

It is quite possible for us to ignore the warnings especially when we “copy and paste” initial configurations in bulk onto a new Nexus switches.

It would now cause an outage after 120 days of evaluation: a hidden time bomb for your data center.


How to avoid such situation? Here I come up two possible ways.

Do not enable evaluation at all on production systems

By default, evaluation grace periods are not enabled. If you somehow enabled it, you can type “no license grace-period” command to avoid activating any evaluations by mistakes.

I suggest this command to be done BEFORE applying any new production configuration. If some features are in use for evaluation, they will also stop working after executing this command.

Use “show license usage” before leaving or acceptance

This command “show license usage” would show the expiration date of each features. A typical output would be something like this.

switch# show license usage
Feature                      Ins  Lic   Status Expiry Date Comments
                                 Count
--------------------------------------------------------------------------------
LAN_ADVANCED_SERVICES_PKG     Yes   -   In use Never       -
LAN_ENTERPRISE_SERVICES_PKG   No    -   In use             Grace 119D 22H
--------------------------------------------------------------------------------

As you can see, "LAN_ENTERPRISE_SERVICES_PKG" is in evaluation, with grace period of around 119 days.

You are now reminded to install the required license file after seeing this.

[References]

Configuring the Grace Period Feature