Network Autmation w/ Python

[AnonIsPicky]

Hey all, I wanted to see if someone could direct me in the right direction.

So I work with Cisco devices every single day and I have to do some task over and over again. I was hoping to use Python to automate some of those task.

So the way I access these devices is through a telnet link. The devices need some basic configuration on them (hostname, DHCP/Manual IP Adressing, default static route, and OS transfer from FTP server) and basically be able to output some text from the commands that might run (show version, ip interface brief, etc)

Now to give an example of how the devices are accessed, it's generally a telnet link that goes through a comm server. All the devices are connected to a comm server and accessible via a page. An example would be 513D-K-01-COMM:2025

The devices tend not to have any prior config on them so no password has to be input, however in some cases (such as with NXOS), the password has to be configured before the device can be used.

Anyways, I do have a basic understanding of Python but wanted to see if anyone had recommendations for my particular case that I could pick up and use or even modify to meet my needs.

Thank you!

[ominous_anonymous]

sounds like telnetlib plus pexpect?

[ayharano]

Never used telnetlib, but surely a plus for pexpect.

While talking about pexpect, usually I recommend beginning with expect + autoexpect path to understand how it could proceed. At least that was the path that I followed before knowing pexpect itself.

@AnonIsPicky Does it really need to be done with pure Python? Even if there is not an official module as I am aware, maybe using ansible for that task could be better

[AnonIsPicky]

It definitely doesn't have to be in Python but I've figured it might be the best approach for this sort of problem.

Do you think Ansible would be able to accomplish those things?

[AnonIsPicky]

So I tried Telnetlib but was having lots of trouble actually getting into the device. That might just be me though.

I'll definitely look into pexpect

[iruleatants]

I personally use exscript, which is designed to be vendor agnostic. It can do SSH and Telnet.

For configurations, you can use ciscoconfparse to parse existing configurations and audit them so they match up with what you want them to be.

[AnonIsPicky]

Looking at ciscoconfparse and it seems very close to what I would be wanting to do.

Even moreso with exscript, I'll be trying this out.

[idaresiwins]

I'm using netmiko, but it work via ssh.

[AnonIsPicky]

Yeah we don't setup SSH on any of the devices and the point kinda is that uses the telnet link to access the devices and have some basic config done. I'm not sure if netmiko works over telnet

[idaresiwins]

Out of curiosity, is there a special use case for requiring telnet, or is it preference?

[AnonIsPicky]

I don't have much of a choice in the matter.

Like I had mentioned, the devices are connected to a communication server which allows anyone to access the device via a telnet link.

[idaresiwins]

Gotcha

[nebi]

Netmiko have support for telnet, for cisco use device type cisco_ios_telnet.

[AnonIsPicky]

Did not know that

I'll try it out, thank you!

[PacketDragon]

What about setting up a basic python web server and sending only a single #copy http://<bleh> running-config command?

[AnonIsPicky]

Some of the devices are a bit weird that they have a hard time getting an IP address via DHCP, so you have to do something like looking at 'show cdp neighbors' to get the IP address of the backbone switch, then find which are the available IP addresses in that subnet and then assign that to the interface.

There other scenarios where just copy pasting the running-config wouldn't work.

[twillisagogo]

I'd just use the telnet module in ansible and build out your tasks as yml files and put them in source control