nmcli Network Tool

May 2021

Overview

A customer had made lots of changes to the network interfaces on a unit and was having a lot of issues, performing an ip a displayed the interface names and IP addresses, and this looked normal.
However, using the nmcli tool told a slightly different story.

nmcli

While nmcli may have many uses, I want to focus on just one. This is not a how to fix your network, this is just highlighting a good use for nmcli. Running nmcli displayed the following output:

nmcli con
NAME UUID TYPE DEVICE
eth0 d9ced338-a402-60eb-c131-0fd3ab4b5ab7 ethernet eth5
eth1 84d43311-57c8-8986-f205-9c78cd6ef5d2 ethernet eth4
eth2 ee7189fe-a32a-4873-bf26-145d4e19a51d ethernet eth0
eth4 3a73717e-65ab-93e8-b518-24f5af32dc0d ethernet eth1
eth5 841334f5-7d18-33f9-86f1-84cee61678a0 ethernet eth3
eth3 c5ca8081-6db2-4602-4b46-d771f4330a6d ethernet --

If you look at the above output, you can see that the NAME and DEVICE are not aligned. eth0 is listed as device eth5, in fact none of interface names and devices are aligned.
The problem was in the ifcfg-ethx files, and once this was fixed (the eth name and mac address in each file was incorrect).
After fixing this issue, running nmcli again gave the following output:

nmcli con
NAME UUID TYPE DEVICE
eth0 d9ced338-a402-60eb-c131-0fd3ab4b5ab7 ethernet eth5
eth1 84d43311-57c8-8986-f205-9c78cd6ef5d2 ethernet eth4
eth2 ee7189fe-a32a-4873-bf26-145d4e19a51d ethernet eth0
eth4 3a73717e-65ab-93e8-b518-24f5af32dc0d ethernet eth1
eth5 841334f5-7d18-33f9-86f1-84cee61678a0 ethernet eth3
eth3 c5ca8081-6db2-4602-4b46-d771f4330a6d ethernet --