Clearpath Insights: Managed Services | Cloud Services | IT Solutions

7 Things to Remember the First Time You Configure a Nexus 7000

The first time I logged into a Nexus 7000, I was a bit intimidated, as there were enough differences between it and the 6500s that I had been more comfortable with in the past. Here are some tips to try and make the transition a little easier.

1. cli alias name wr copy run start
This is actually the first thing I type into any Nexus that I configure. I know that Cisco is trying to train engineers to get out of the habit of using wr and, instead, wasting characters by typing out the more formal copy running-config startup-config I prefer to find alternate ways around the problem.

2. The base VDC should always be left as an administrative VDC
Presuming that you've purchased the VDC licensing (because who doesn't want 3 extra Nexii for the low cost of an additional license), you should leave the baseline VDC free of production configuration. This allows you to manipulate resource availability and restart VDCs without running the risk of impacting a larger segment of the environment.

3. If you can't find a command, check which features are enabled
NX-OS is definitely a divergence from traditional IOS. By default, configuration commands are not visible unless the feature is enabled. This allows for a number of benefits, such as limiting the exposure of a switch to vulnerabilities or unexpected features in code, but also can prove to be a frustrating experience. Everything from SSH to SVIs must be individually enabled.

4. ISSU is your friend
Another change from (most forms) of traditional IOS is the availability of in-service software updates. ISSU allows engineers to perform mostly hitless upgrades of NX-OS within a major software release (as always, YMMV, and you should check the release notes of the version to which you are updating to make sure there aren't any hidden gremlins lying in wait). In my personal experience, unless the EPLD is also being upgraded, I've never noticed impact. This will allow you to upgrade more frequently and with less impact than in the days when reload was an integral part of the upgrade process.

5. Show run | section eigrp -> show run eigrp
NX-OS has made some commands more efficient. If you're interested in seeing a subsection of the (admittedly large) configuration, you can type show run <section name> and you will most likely find the droids you are looking for.

6. VDCs are not connected via the backplane
Make sure you plan for physical connections between VDCs. This leads to amusing scenarios where you could be running a cable from one port on a line card directly back to the same line card. While it may appear somewhat counter-intuitive, it is certainly correct.

7. Wireshark is built in
The command ethanalyzer is basically a port of wireshark to NX-OS. It uses tcpdump syntax and wireshark filter commands to allow an engineer to get a detailed view of traffic passing through the Nexus. It will add about 5% utilization to your CPU, so keep that in mind, but it is definitely a powerful tool.


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