My own config generator and autoloader part 1 – preparing the config

Hello again

It’s been a while since my last entry and i blame covid 🙂

Jokes aside, I used that 4 month break to do some thinking about where I want to be in a few years’ time. I kept learning python and watching how networks become more devops-oriented. The harsh reality is that most of network engineers will either lose their jobs or become programmers. There’s no denying that at this point.  Also, I personally feel that i’m a bit tired of good old network configuration (which is why i never did my ccie) and it’s time to make another step forward, just like 9 years ago when I joined the sonicwall support team. From now on my posts will concentrate more on how to automate operations rather than on operations per se.

Let’s start, then.

Part of what i do at work has to do with configuring new routers and sending them to client sites. I get a telnet connection through a console server to those routers, which isn’t ideal. Part 1 is coming up with the actual config, which is always a pain because you need to replace the config in a number of places. I’ve therefore come up with the following python script which:

  1. opens a GUI where you can put your config variables
  2. generates a config and saves the result to a test.txt file on the desktop
  3. archives the config as a <hostname>.txt file on the desktop
from networkconfgen import NetworkConfGen
import sys
import os

import PySimpleGUI as sg
import shutil
import socket
from tkinter import *
from tkinter import messagebox

#this creates the GUI layout 


layout = [[sg.Text('My config generator')], 
[sg.Text('LAN IP', size=(21, 2)),sg.InputText('x.y.z.a'),sg.Text('subnet mask', size=(18, 2)),sg.InputText('')], 
[sg.Text('WAN IP', size=(21, 2)),sg.InputText('a.s.d.f'),sg.Text('subnet mask', size=(12, 2)),sg.InputText('')],
[sg.Text('hostname', size=(21, 2)),sg.InputText('testrouter')],
[sg.Text('VRRP IP', size=(21, 2)),sg.InputText('x.y.z.b')],
[sg.Text('WAN next hop', size=(21, 2)),sg.InputText()],
[sg.Text('Serial Number', size=(21, 2)),sg.InputText('BIGBROWNFOX')],
[sg.Text('tunnel1 IP', size=(21, 2)),sg.InputText('172.16.0.x'),sg.Text('subnet mask', size=(12, 2)),sg.InputText('')],
[sg.Text('tunnel2 IP', size=(21, 2)),sg.InputText('172.16.1.x'),sg.Text('subnet mask', size=(12, 2)),sg.InputText('')],
[sg.Text('loopback', size=(21, 2)),sg.InputText('172.16.2.x'),sg.Text('subnet mask', size=(12, 2)),sg.InputText('')],
[sg.Text('network address of LAN', size=(21, 2)),sg.InputText('x.y.z.0'),sg.Text('subnet mask in slash format', size=(12, 2)),sg.InputText('/29')],

window = sg.Window('Window Title', layout) 
event, values =

#this reads the variables from the array generated by the GUI. 
lanip = values[0] 
lanipsubnetmask = values [1] 
wanip = values[2]
wanipsubnetmask = values [3]
hostname = values[4]
virtlanip = values[5]
nexthop = values[6]
serial = values[7]
tunnel1 = values[8]
tunnel1subnetmask = values[9]
tunnel2 = values[10]
tunnel2subnetmask = values[11]
loopback = values[12]
loopbacksubnetmask = values[13]
networklan = values[14]
networklansubnetmask = values[15]

#this checks if values in all fields are valid IP addresses

# legal
except socket.error:
messagebox.showerror(title="OH BLIMEY", message="ADDRESSING MISTAKE")


#this creates a confgen object

confgen = NetworkConfGen()

template = """

#here put any configuration you need with variables in the double brackets, example:
hostname {{hostname}}

interface Gi0/0
ip address {{WANIP}} {{WANIPSUNETMASK}}
parameters = {
"hostname": hostname, 
"WANIP": wanip,
"WANIPSUBNETMASK": wanipsubnetmask,
"REALLANIP": lanip,
"REALLANIPSUBNETMASK": lanipsubnetmask,
"VIRTLANIP": virtlanip,
"NEXTHOPWANIP": nexthop,
"SERIAL": serial,
"TUNNEL1IP": tunnel1,
"TUNNEL1IPSUBNETMASK": tunnel1subnetmask,
"TUNNEL2IP": tunnel2,
"TUNNEL2SUBNETMASK": tunnel2subnetmask,
"LOOPBACKIP": loopback,
"LOOPBACKIPSUBNETMASK": loopbacksubnetmask,
"NETWORKLAN": networklan,
"NETWORKLANSUBNETMASK": networklansubnetmask
result = confgen.render_from_string(
if not result.render_error:
sys.stdout = open("test.txt", "w")

print("Something went wrong: %s" % result.error_text)

oldname = 'test.txt'


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