Archive for the ‘python’ Category

In VRF-lite situation multiple customers are connected to the same CE (each customer belongs to different vrf)
Now in this design wan circuit is moving from old PE to new PE.

During this bulk migration we need to replace static route pointing to OLD PE and with static route pointing to new PE for every customer

This migration related Pre and Post data such as vrf,CE wan ip,customer name,PE name etc. is recorded in excel sheet

With help of library xlrd , ciscoconfparse we can automate the script generation for static route which can be used during migration

we are reading all info for each VRF such as (VRF,OLD_WAN_IP,NEW_WAN_INT) by running FOR Loop on excel and storing it in dictionary

e.g Below 2 static routes needs to be replaced with new wan interface and new wan IP

ip route vrf ABC 10.10.10.10 255.255.255.255 Serial1/0.10 192.168.1.1
ip route vrf ABC 10.10.10.20 255.255.255.255 Serial1/0.10 192.168.1.1

Logic for the python code is
1. Get the static routes from router config for each vrf (one by one) using OLD wan IP (regular expression)
2. Take one IP route at a time and create list using split method so we will get 8 elements in list from 0-7
3. Pop the elements from the list till list contains only 6 elements from 0-5 (remove old interface and old wan ip)
4. Append new wan interface and then new wan PE IP to the list
5. Prepend no to the old static route and print it
6. Using join method on the list create new static route pointing to new wan IP and interface and print it

output is

no ip route vrf ABC 10.10.10.10 255.255.255.255 Serial1/0.10 192.168.1.1
ip route vrf ABC 10.10.10.10 255.255.255.255 FastEthernet0/1.10 192.168.2.1
!

no ip route vrf ABC 10.10.10.20 255.255.255.255 Serial1/0.10 192.168.1.1
ip route vrf ABC 10.10.10.20 255.255.255.255 FastEthernet0/1.10 192.168.2.1
!

python code for static route script for bulk migration.

import xlrd
from ciscoconfparse import CiscoConfParse

# provide config file path
routerconfig = CiscoConfParse(configfilepath)
wanip = c[‘OLD_WAN_IP’].split(“.”)

# result [192,168,1,1]
wanipregex = “\.”.join(wanip)
# result 192\.168\.1\.1
a = “^ip route vrf ” + c[‘VRF’] +”(.+?)” + wanipregex
# result ^ip route vrf ABC(.+?)192\.168\.1\.1

# running for loop over list of static routes for vrf ABC 2 routes in this case
for staticroute in routerconfig.find_objects(a):
line = staticroute.text

sroute = line.split(” “)
# result [ip, route, vrf, ABC, 10.10.10.10, 255.255.255.255, Serial1/0.10, 192.168.1.1]

while len(sroute) > 6:
sroute.pop()

# result [ip, route, vrf, ABC, 10.10.10.10, 255.255.255.255]

sroute.append(c[‘NEW_WAN_INT’])
# result [ip, route, vrf, ABC, 10.10.10.10, 255.255.255.255,FastEthernet0/1.10,]
sroute.append(c[‘NEW_PE_WAN_IP’])
#result [ip, route, vrf, ABC, 10.10.10.10, 255.255.255.255, FastEthernet0/1.10, 192.168.2.1]
print “no ” + line
# result no ip route vrf ABC 10.10.10.10 255.255.255.255 Serial1/0.10 192.168.1.1
print ” “.join(sroute)
# result ip route vrf ABC 10.10.10.10 255.255.255.255 FastEthernet0/1.10 192.168.2.1
print “!”

Netmiko is Multi-vendor library to simplify Paramiko SSH connections to network devices with the help of netmiko library we can do network automation using python
https://github.com/ktbyers/netmiko

In some situations we can not directly connect to network devices like router and switches. We can only access them via jump server
If we have Linux machine from where are initiating ssh connection and jump server is also Linux

Linux(script server)—–Linux(jump server)—–Router

Then we can use Linux ProxyCommand to access devices via jump server.
Below link provides detail for Netmiko SSH Proxy Support
https://pynet.twb-tech.com/blog/automation/netmiko-proxy.html

But we can not use proxycommand if script server is windows

windows(script server)—–Linux(jump server)—–Router

Below code can be use in this situation
In this code i tried to get device up time via jump server using redispatch(Netmiko 1.3.0 Release). Need to adjust global_delay_factor by doing trail and error method

from netmiko import ConnectHandler
import time
from netmiko import redispatch

jumpserver = {‘device_type’: ‘terminal_server’,’ip’: ‘x.x.x.x’,’username’: ‘name’,’password’: ‘pass’,’global_delay_factor’:5}

net_connect = ConnectHandler(**jumpserver)
print net_connect.find_prompt()

net_connect.write_channel(‘command to access router’)
time.sleep(1)
net_connect.read_channel()

redispatch(net_connect, device_type=’cisco_ios’)
net_connect.send_command(‘show version | i uptime’)