Automation for Networkers

Today, I like to write about a small and very basic topic. I think everybody requires from time to time the output of certain CLI commands on a set of devices, e.g. for troubleshooting. Quite often, no direct access to the devices is possible, therefore you need to ask somebody else to collect the data. In many cases, you just get plain session logs from e.g. putty and they are in many cases quite unstructured.

In my last post, I took a look on how to parse information from a Cisco IOS configuration using regular expressions. This post focuses on the same use case as the last one, but this time I use the ciscoconfparse library. The use of the library doesn't mean that you can ignore regular expressions at all. You need at least a basic understanding of it. Before continuing, I highly recommend to read my last post about Parse Cisco IOS configurations using RegEx. I will reuse some of the RegEx and skip the detailed explanation in this post.

In one of my earlier posts, I parse IP parameters from an existing Cisco IOS configuration using ciscoconfparse. In this post, I'll like to provide some basic patterns how to parse (almost any) information from a running configuration, but first without using any library. I just take a look at the python standard library and regular expressions (RegEx).

Today, I like to show you an example how to automate SSH connections with netmiko. To demonstrate it, I decide to create a simple CDP information crawler. The result should be a basic network diagram based on HTML and Javascript. As you might know, this involve more components than just netmiko. It is used to collect the information from the device using SSH. To parse the output from the device, we will use TextFSM. For the visualization, we will use some HTML, Javascript and CSS.

Today I'd like to show you another use case using the ciscoconfparse python module. During the migration from a Cisco VSS to a Cisco Nexus vPC pair, I need to translate a lot of static ARP entries from an existing configuration. To do this translation manually is not very effective, because the configuration is expressed differently in NX-OS compared to Cisco IOS. From my perspective, this is an ideal case for ciscoconfparse and python.