THAI CPE

• list1 =['phy','chem',1997,'2001']
  print 'list before update: ',list1
  list1[2] = 2000
  list1[3] = 2020
  print 'list after update: ',list1

• tup1 = ('physics', 'chemistry', 1997, 2000);
• tup2 = (1, 2, 3, 4, 5, 6, 7);
• tup3 = "a", "b", "c", "d";
• 
  
• print "tup1[0]: ", tup1[0]
• print "tup2[1:5]: ", tup2[1:5]
  

• tup1 = ();

• tup1 = (50,);

• del tuple;

• dict = {'Name': 'Zara', 'Age': 7, 'Class': 'First'};
• 
  
• print "dict['Name']: ", dict['Name']

Updating Dictionary

• dict['Age'] = 8; # update existing entry
• dict['School'] = "DPS School"; # Add new entry

>>> dict = {'Name' : 'Zara','Age' : 7, 'Class' : 'first'}
>>> type(dict)
<type 'dict'>
>>> list1 = {'Name' : 'Zara','Age' : 7, 'Class' : 'first'}
>>> type(list1)
<type 'dict'>
>>> dict
{'Age': 7, 'Name': 'Zara', 'Class': 'first'}
>>> dict['Age']
7
>>> dict['age']
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'age'
>>> dict['Age']=10
>>> dict
{'Age': 10, 'Name': 'Zara', 'Class': 'first'}
>>> dict['Class'] = 'Fifth'
>>> dict
{'Age': 10, 'Name': 'Zara', 'Class': 'Fifth'}
>>> del dict['Class']
>>> dict
{'Age': 10, 'Name': 'Zara'}

• Suppose list1 is [3, 5, 25, 1, 3], min(list1) is 1.
  min returns the minimum element in the list.
  
  
• Use function random.shuffle(list1) to shuffle the list(say list1).
  
  
• Suppose list1 is [1, 5, 9, sum(list1) is 15.
  Sum returns the sum of all elements in the list.
  
  
• A class is a user-defined datatype, not a core datatype.
  
  
• L = [1, 23, 'hello', 1], datatype is List.
  List datatype can store any values within it.

• for iterating_var in sequence:
  
•   statement(s)
• 
  
• for letter in 'Python':
•   print 'Current Letter :', letter
• 
  
• fruits = ['banana', 'apple', 'mango']
• for fruit in fruits:
•   print 'Current fruit :', fruit

5. forloops.py

• fruits = ['banana', 'apple', 'mango', 'orange', 'berry']
  
  for i in fruits:
      print 'Current the fruit is ', i
      print 'Goodbye'
  print 'type = ', type(i)
  
  for letter in 'Python':
      print 'Current Letter = ', letter
  print 'Goodbye'

C:\Python27>python forloops.py
Current the fruit is  banana
Goodbye
Current the fruit is  apple
Goodbye
Current the fruit is  mango
Goodbye
Current the fruit is  orange
Goodbye
Current the fruit is  berry
Goodbye
type =  <type 'str'>
Current Letter =  P
Current Letter =  y
Current Letter =  t
Current Letter =  h
Current Letter =  o
Current Letter =  n
Goodbye

• while expression:
•   statement(s)
• 
  
• count = 0
• while (count < 9):
•   print 'The count is:', count
•   count = count + 1
• 
  
• print "Goodbye!"

6. Whileloops.py

• count = 0
  while (count < 9):
      print 'The count is:', count
      count = count + 1
  print "Loop has done!"

C:\Python27>python Whileloops.py
The count is: 0
The count is: 1
The count is: 2
The count is: 3
The count is: 4
The count is: 5
The count is: 6
The count is: 7
The count is: 8
Loop has done!

• for iterating_var in sequence:
•   for iterating_var in sequence:
•     statements(s)
•   statements(s)
• 
  
• while expression:
•   while expression:
•     statement(s)
•   statement(s)

7. nest.py

• for i in range(1,5):
      for j in range(1,3):
          print "j=",j
      print " *i=",i
  print "loops done"

C:\Python27>python nest.py
j= 1
j= 2
 *i= 1
j= 1
j= 2
 *i= 2
j= 1
j= 2
 *i= 3
j= 1
j= 2
 *i= 4
loops done

• x = ['ab', 'cd']
  for i in x:
    i.upper()
  print(x)
  Output: ['ab','cd']
  The function upper() does not modify a string in place, it returns a new string which isn't being stored anywhere.
  
  
• i=1
  while True:
    if i%007 == 0:
      break
    print(i)
    i += 1
  Output: 1 2 3 4 5 6

Invalid Coins:

• num_coins = len(coin_value)
  print coin_value, num_coins
  count = 0
  
  while count < num_coins: # step each look for invalid
      current_value = coin_value[count]
      coin_amt = int(current_value)
      print 'count = ', count, 'Coin Amount = ', coin_amt
      count += 1
      if coin_amt not in (quarter, dime, nickel, penny):
          print 'An Invalid coin was detected'
          count = 0
          coin_value = 0
          num_coins = 0
          coin_amt = 0
          coin_value = input('enter coin values')
          num_coins = len(coin_value)

C:\Python27>python proj1.py
This item costs  54
**Enter coins in form 1,5,10,25,..
enter coin values 5,5,1,1,12,10
(5, 5, 1, 1, 12, 10) 6
count =  0 Coin Amount =  5
count =  1 Coin Amount =  5
count =  2 Coin Amount =  1
count =  3 Coin Amount =  1
count =  4 Coin Amount =  12
An Invalid coin was detected
enter coin values 5,5,1,1,10
count =  0 Coin Amount =  5
count =  1 Coin Amount =  5
count =  2 Coin Amount =  1
count =  3 Coin Amount =  1
count =  4 Coin Amount =  10

Coin Count:

• total_quarters = 0    #This is setting coin count to zero only
  total_dimes = 0
  total_nickels = 0
  total_pennies = 0
  
  print coin_value, num_coins
  
  while count < num_coins:    # step each look for invalid
      current_value = coin_value[count]
      coin_amt = int(current_value)
      print 'count = ', count, 'Coin Amount = ', coin_amt
      count += 1
  
      if coin_amt not in (quarter, dime, nickel, penny):
          print 'An Invalid coin was detected'
          count = 0
          coin_value = 0
          num_coins = 0
          coin_amt = 0
  
          total_quarters = 0    #This is setting coin count to zero only
          total_dimes = 0    #need to deduct the coins returned
          total_nickels = 0    #need to fix this.
          total_pennies = 0
  
          coin_value = input('enter coin values ')
          num_coins = len(coin_value)
  
      elif coin_amt == 25:
          total_quarters += 1
      elif coin_amt == 10:
          total_dimes += 1
      elif coin_amt == 5:
          total_nickels += 1
      elif coin_amt == 1:
          total_pennies += 1
  
  coin_count = (total_quarters, total_dimes, total_nickels, total_pennies)
  total_value = total_quarters * 25 + total_dimes * 10 + total_nickels * 5 + total_pennies
  
  print 'Coin count = q,d,n,p ' ,coin_count
  print 'Total value =',total_value

C:\Python27>python proj1.py
This item costs  54
**Enter coins in form 1,5,10,25,..
enter coin values 5,10,5,10
(5, 10, 5, 10) 4
count =  0 Coin Amount =  5
count =  1 Coin Amount =  10
count =  2 Coin Amount =  5
count =  3 Coin Amount =  10
Coin count = q,d,n,p  (0, 2, 2, 0)
Total value = 30

Make a decision:

• done = 0
  
  while done == 0:
      while count < num_coins:    # step each look for invalid
          current_value = coin_value[count]
          coin_amt = int(current_value)
          print 'count = ', count, 'Coin Amount = ', coin_amt
          count += 1
          if coin_amt not in (quarter, dime, nickel, penny):
      ...
      print 'Total value =',total_value
  
      # 3 conditions
  
      if item_cost == total_value:
          # done
          print 'Thank you please take your item'
          done = 1
      elif item_cost < total_value:
          # return change
          return_change = total_value - item_cost
          # *update coin count*
          print 'Please take your change of ',return_change
          print 'Still need to update coin count'
          done = 1
      elif item_cost > total_value:
          # input more coins
          item_cost = item_cost - total_value
          # *Do everything over until done*
          print 'Not enough money please enter ',item_cost
          count = 0
          coin_value = 0
          num_coins = 0
          coin_amt = 0
          total_quarters = 0 # fix this total as well
          total_dimes = 0
          total_nickels = 0
          total_pennies = 0
          coin_value = input('enter coin values')
          num_coins = len(coin_value)

C:\Python27>python proj1.py
This item costs  54
**Enter coins in form 1,5,10,25,..
enter coin values 25,25,1,1,1,1
(25, 25, 1, 1, 1, 1) 6
count =  0 Coin Amount =  25
count =  1 Coin Amount =  25
count =  2 Coin Amount =  1
count =  3 Coin Amount =  1
count =  4 Coin Amount =  1
count =  5 Coin Amount =  1
Coin count = q,d,n,p  (2, 0, 0, 4)
Total value = 54
Thank you please take your item

C:\Python27>python proj1.py
This item costs  54
**Enter coins in form 1,5,10,25,..
enter coin values 25,25,10
(25, 25, 10) 3
count =  0 Coin Amount =  25
count =  1 Coin Amount =  25
count =  2 Coin Amount =  10
Coin count = q,d,n,p  (2, 1, 0, 0)
Total value = 60
Please take your change of  6
Still need to update coin count

C:\Python27>python proj1.py
This item costs  54
**Enter coins in form 1,5,10,25,..
enter coin values 25,25
(25, 25) 2
count =  0 Coin Amount =  25
count =  1 Coin Amount =  25
Coin count = q,d,n,p  (2, 0, 0, 0)
Total value = 50
Not enough money please enter  4
enter coin values 1,1,1,1
count =  0 Coin Amount =  1
count =  1 Coin Amount =  1
count =  2 Coin Amount =  1
count =  3 Coin Amount =  1
Coin count = q,d,n,p  (0, 0, 0, 4)
Total value = 4
Thank you please take your item

• import telnetlib
  import time
  
  def telnet_gns3(ip):
      wait = .2
     
      connection = telnetlib.Telnet(ip, 23, 5)
     
      output = connection.read_until("Password:", 5)
      connection.write('cisco' + "\n")
      connection.write('ena' + "\n")
     
      output = connection.read_until("Password:", 5)
      connection.write('cisco' + "\n")
      time.sleep(wait)
     
      connection.write("conf term" + "\n")
      time.sleep(wait)
      connection.write("int f0/0" + "\n")
      time.sleep(wait)
      connection.write("ip add 6.5.5.5 255.0.0.0" + "\n")
      time.sleep(wait)
      connection.write("end" + "\n")
     
      time.sleep(wait)
      connection.write("sho ip int brief" + "\n")
      time.sleep(wait)
     
      output = connection.read_very_eager()
      print output
     
      connection.close()
     
  #Call gns3
  telnet_gns3('192.168.56.101')
  

• ...
      output = connection.read_very_eager()
      # - Write output to a file -
      ESW1 = open("ESW1", "w")
      ESW1.write(output)
      ESW1.close
      print output
  ...

upload.i4th.in.th/th/download.php?id=59493B941

22. TN7.py

• import telnetlib
  import time
  
  def telnet_gns3(ip):
      wait = 5
      # -Sign in-
      connection = telnetlib.Telnet(ip, 23, 5)
      connection.read_until("Password:", 5)
      connection.write('cisco' + "\n")
      connection.write('ena' + "\n")
      connection.read_until("Password:", 5)
      connection.write('cisco' + "\n")
      # -Sign in-
     
      # -Command loop-
      cmd_file = raw_input('Enter command file name and extension: ')
      selected_cmd_file = open(cmd_file, 'r')
      selected_cmd_file.seek(0)
      for each_line in selected_cmd_file.readlines():
          time.sleep(wait)
          connection.write(each_line)
          connection.write("\n")
      # -Command loop-
     
      # -Write output to a file-
      time.sleep(wait)
      output = connection.read_very_eager()
      ESW1 = open("ESW1", "w")
      ESW1.write(output)
      ESW1.close
      # -Write output to a file-
      print output
     
      connection.close()
     
  #Call gns3
  telnet_gns3('192.168.56.101')

testcmds.txt

• conf term
  int f0/0
  ip add 5.5.5.5 255.0.0.0
  end
  sho ip int brief
  sho run
  

C:\Python27>python TN7.py
Enter command file name and extension: testcmds.txt

ESW1#conf term
Enter configuration commands, one per line.  End with CNTL/Z.
ESW1(config)#
ESW1(config)#int f0/0
ESW1(config-if)#
ESW1(config-if)#ip add 5.5.5.5 255.0.0.0
ESW1(config-if)#
ESW1(config-if)#end
ESW1#
ESW1#sho ip int brief
Interface                  IP-Address      OK? Method Status                Protocol
FastEthernet0/0            5.5.5.5         YES manual administratively down down
FastEthernet0/1            192.168.56.101  YES manual up                    up
...
upload.i4th.in.th/th/download.php?id=594E30291

The Network at the Center of Every Evolution Step: Managing Your Career Through Key Market Transitions

Industry Relevant Bridge the Knowledge Gaps

Centralized > Silo'd > Unconnected > Network as Platform > Internet of Everything

• Growing IT Talent Gaps
• Re-skilling Needed
• Evolving Job Roles By Industry
• Programmability Skills Required
• Business Skills In Demand
  
  
• Business requirements for globalization, flexibility, speed
• Line of Business involvement in IT spending
• Consumerization of IT - software-based services
• Disruptive technologies: cloud, mobility, social, video, Big Data

Networker Responsibilities are Growing and Shifting:

Responsibility Focus:

• Increase of Design
• Decrease of Deploy
• Decrease of Operate
• Increase of Optimize
• Innovate
  
  
• WAN, WLAN, Routers, Switches, UC, L4-7
• Compute/Storage, Security, NFV, Orchestrators, Controllers, Hypervisors, Analytics, Automation, Transformation

<- Speeds - Users - Data Center - Mobile - Cloud - Threats - Big Data - Internet Of Things - SDN ->

Network Programmability in a Programmable Networking Environment:

• Network Users:
  
  • User-identifier (tenant/user)
  • Application
  • Location Device Type
    
    
• Policy Properties:
  
  • Policy Creator
  • Policy Name
  • Policy Scope
  • Policy Priority
  • Policy Time:
    
    • Start Time
    • End Time
    • Hard timeout
    • Idle timeout
    • recurrence
      
      
• Resources:
  
  • User-identifier (tenant/user)
  • Application
  • Device Type
  • Location
    
    
• Actions:
  
  • Permit
  • Deny
  • Copy
  • Monitor
  • Redirect (L3, L4, L7)
  • No copy
  • No redirect
    
    
• Action Properties:
  
  • Priority Level
  • Resource Level
  • Experience Level
  • Trust Level
  • Destination
  • Sample Rate
    
    
• High-Level Business Intent Policies
• Automatically converted to Network Language
• Conflict Detection and Resolution
• Extensible
• Supports different patterns of policies:
  
  • Access Policies
  • Source-Destination Directional Policies
  • Event - Condition - Action
  • Includes Collections (Ex: a group of user ids, a group of applications, etc.)
  • Choose custom tags for policies
  • Choose multiple attributes in each category

Abstracting Conventional Policy Complexity:

• Conventional Model:
  Admin Driven [
  
  • The What "Security Policy for Branch A"
  • The How "Change ACLs in the Following Elements" ->
• ACI Policy Model:
  
  • The What "Security Policy" - Admin Driven
  • ACI Constructs - Northbound APIs
  • The How "Change ACLs in the Following Elements" - APIC EM ]

ACI Abstracts System Management and Enables Programmable Driven Policies

Move from micro-managing "boxes" to a policy-driven, holistic view of the network

Proactive Network Applications: Automate Network Provisioning

Key Use Cases:

• Agile Network Provisioning
• Device Health Monitoring
• Auditing/Compliance

Key Skills:

• REST
• NETCONF/YANG
• Puppet/Chef (DC)
• C, JAVA, Python
  
  

• Security
• Dynamic QoS
• Traffic Steering

Key Skills:

• C, JAVA, or Python
• REST
  
  

• CLI config
• Scalability
• Resiliency
• Stability
• Availability
• Stuck in the DC
  
  
• Code
• Agility
• Automation
• Testing
• Advanced Tools
• Coding where you like

Development Economics - Deploying a physical network test-bed requires:

• Equipment about $2,000/node
• Setup about 1-2 hours per network
• Expertise level high @ about $100/hour for CCNA
• Resources must be dedicated, scheduled

Time and money you probably don't have

VIRL can help simplify and streamline development processes and environments

What is VIRL? - A network orchestration and virtualization platform that enables:

• Point-and-click network design
• Painless configuration
• Integration of platform-sync'd code
• Rapid setup and tear-down
• Seamless connectivity with 'real' networks
• Portability and repeatability

Virtualized Network Operating Systems:

• IOS-XRv: IOS XR v5.1.3 and v5.2.0
• NX-OSv: NX-OS v7.1(0)ZD
• CSR1000v: IOS XE v15.4(3S_XE313)
• IOSv: IOS v15.4(1.20T)
• Servers: Ubuntu 14.04 LTS

The Wall of Confusion: Or, why can't we all just get on together?

• Development: I want to change!
• Operations: I want stability!

DevOps Virtuous Cycle:

• Increased Reliability
• Higher Quality
• Improved Maintain-ability
• Faster Releases
• Increased Innovation
• Improved Scalability
• Increased Proactivity

Aspects of DevOps - Agile Development and CI/CD:

Continuous Integration and Deployment in the Development Cycle:

• Build Automation
• Virtual Environments
• Reporting and Visibility
• Artefact Management
• Coding and Refactoring
• Source Code Management

Introducing DevNet: Creating a Community of Software Developers who Leverage Cisco Technology in Their Work

Enabling a Robust Developer Ecosystem:

• Engineering Platform APIs
• SDKs and Tools
• Developer Support
• Community Management

To Build Compelling and Innovative Apps

• Developer.Cisco.Com
  
  
• devnetsandbox.cisco.com/RM/Topology

#!/usr/bin/env python
import socket
import time
from cisco import *
from argparse import ArgumentParser

parser = ArgumentParser('Server health monitor')
parser.add_argument('-s', '--server', help='IP address of server to monitor', required=True)
parser.add_argument('-p', '--port', help='TCP port to poll', type=int, required=True)
parser.add_argument('-c', '--commands', help='Commands to run if an interface fails, use ; to separate multiple commands', required=True)
args = parser.parse_args()
connected = False
while True:
  try:
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    if sock.connect_ex((socket.gethostbyname(args.server), int(args.port))) == 0:
      connected = True
    sock.close()
  except socket.error:
    connected = False
  if connected == False:
    with open('servermon.log', 'a') as f:
      f.write('The server %s failed on port %s at time %s. Debug output below:' % (args.server, args.port, time.asctime()))
      for cmd in args.commands.split(';'):
        f.write(cli(cmd)[1])
  time.sleep(30)

R1# python servermon.an -s 10.9.46.202 -p 23 -c "show int vlan 20:show proc cpu"

R1# show file bootflash:servermon.log

• In this paradigm, the fundamental concept of an underlay and overlay abstraction gained widespread acceptance (exemplified by IP forwarding and the overlay abstraction of MPLS).
  
  

• NOC engineers log into a switch and run the same commands day-in, day-out
• These are talented individuals whose time is money
• How can we code our way out of this?
• Let's combine multi-command tasks into super-commands

#!/usr/bin/env python
from cisco import *
from argparse import ArgumentParser

parser = ArgumentParser('Supercommand')
parser.add_argument('ip')
args = parser.parse_args()
ip = args.ip

for arp in CLI('show ip arp %s' % (ip), do_print=False).get_output():
  if ip in arp: break
else:
  raise Exception('Unable to find %s in ARP output' % ip)

ip, timer, mac, interface = arp.split()

for cam in CLI('show mac address-table address %s' % (mac), do_print=False).get_output():
  if mac in cam: break
else:
  raise Exception('Unable to find %s in CAM output' % mac)

cam_fields = cam.split()
if cam_fields[0] == '*': cam_fields.pop(0)
vlan, mac, entrytype, age, secure, ntfy, port = cam_fields

for cdp in CLI('show cdp neighbor interface %s' % (port), do_print=False).get_output():
  if port in cdp: break
else:
  raise Exception('Unable to find %s in CDP output' % port)

print('Here is some information on %s:' % ip)
print(' ' * 4 + 'MAC address: %s' % mac)
print(' ' * 4 + 'Local interface: %s' % port)
print(' ' * 4 + 'VLAN: %s' % vlan)
print(' ' * 4 + 'L3 gateway: %s' % interface)
print(' ' * 4 + 'CDP details: %s' % cdp)

R1(config)# cli alias name supercommand python supercommand.py

R1# supercommand 10.9.46.202

• The chief weaknesses of the distributed control model are in the areas of network flexibility and user control (there is not enough granular control over the consensus path selection to provide sufficient flexibility), programmability (there is no standard API to inject state or extract information and most automation is either vendor dependent or heavily embedded with knowledge of vendor configuration/operation command semantics), as well as the high degree of integration of its control, data, service, and management planes (driving a scale upgrade cycle and other dependencies). Elements in this model have only recently begun to experiment with the externalizing the control plane so that the route processor can run on more scalable (and easily upgradeable) compute platforms (that are not bound by the drag introduced in creating specific carriers and fabric interfaces for an in-shelf processor).
  
  
• It could be argued that the recursion through an interaction of the IGP/BGP/MPLS paradigm introduces a good deal of complexity and overhead. However, models are also evolving a number of integrated convergence, high-availability, and black-hole avoidance mechanisms that providers find desirable.
  
  
• Centralizing the control plane in a logically centralized but physically distributed model makes sense from scale, high-availability, and geographical perspectives.
  
  
• SDN advocates can learn from historical attempts at centralization. Two examples are provided; ATM LANE (which is truly historical) and the route server (still used in the IP forwarding domain).

3. Ping a Range:

• Sometimes you need to find a free IP
• Sometimes you need to check which hosts are up, which are down
• Sometimes you only have access to the switch
• How do we code our way out of this?
• Write a python script that will ping a range of IP addresses

#!/usr/bin/env python
import re
from cisco import *
from argparse import ArgumentParser

def expandrange(rnge):
  if '-' in rnge:
    r = rnge.split('-')
    return range(int(r[0]), int(r[1])+1)
  else:
    return [rnge]

parser = ArgumentParser('pingrange')
parser.add_argument('ip')
parser.add_argument('-o', '--options', help='Options to pass to ping, default: count 1', default='count 1')
args = parser.parse_args()
target = args.ip

octets = target.split('.')
for o1 in expandrange(octets[0]):
  for o2 in expandrange(octets[1]):
    for o3 in expandrange(octets[2]):
      for o4 in expandrange(octets[3]):
        ip = '%d.%d.%d.%d' % (int(o1),int(o2),int(o3),int(o4))
        print('%s - ' % ip),
        m = re.search('([0-9\.]+% packet loss)', cli('ping %s %s' % (ip, args.options))[1])
        print m.group(0)

R1# python pingrange.py 10.1.1.1-10

• The LANE system of servers provided the first glimpses into the complexities of high availability in a centralized model. Their high-availability model lacked synchronization and often required the user to manually maintain the LECS database in a specific order. These models significantly increased the scale of the control plane infrastructure (in the form of a very large VCC fan out between servers and elements).
  
  
• The more modern route server and route reflector provide a centralized control point for an otherwise distributed IP control plane. These control points are considered the "opportunity point" for SDN development.

Where do I start?

• Leverage free online resources for learning:
  www.codeacademy.com
  www.coursera.org
  
  
• Practice:
  Find a task you do on a daily basis
  See if you can automate it
  Python runs on all major OS' (including iPhone)
  
  
• Learn from existing scripts:
  github.com/datacenter
  

Standalone versus Controller-based:

Network programmability applications can be proactive or reactive, they can use CLI or NETCONF; they also can be standalone or controller-based.

Standalone applications have the following characteristics and considerations:

• Communication to each device is direct, from your application directly to the device. Compare with controller-based, where communication goes through a translation process as it goes through the controller, before being sent to the device.
  
  

• 'Hello Device'

A simple introductory application that uses the pexpect library and pings a network device.

• Demo!
• Numbers, Strings, and Variables

A quick introduction to Python numbers, strings, and variables.

• Code Blocks

An overview of how code blocks are defined in Python.

• Printing

A brief look at printing variables using Python commands

• Comments

The importance of commenting code, and the mechanisms for doing so.

30. hello-device.py

• Tell Python to use the 'pexpect' library:
  import pexpect
  The import statement tells Python to import all of the functions contained in the external library named pexpect.
  
  
• Set the ping options:
  ping = pexpect.spawn('ping -c 5 localhost')
  pexpect.spawn is using the pexpect library to create, or spawn, a command process. The information inside the parenthesis is telling the spawned process to ping the localhost five times.
  
  
• result = ping.expect([pexpect.EOF, pexpect.TIMEOUT])
  print(ping.before)
  
  * pexpect.spawn and pexpect.run() are not available on Windows, as they rely on Unix pseudoterminals (ptys). Cross-platform code must not use these.
  
  

• 0b10100 -> Binary base
• 0o12  -> Octal
• 98  -> Decimal
• 0x78A4  -> Hexadecimal
  

• Whole numbers (eg 5)
• Can be very large
• Can be negative
• Can be other bases (eg binary, hexadecimal)

Floats:

• Floating point (eg 5.2)
• Exponential notation
• Can be negative
• Represent real numbers
  

Arithmetic operations: +, -, *, /, // (truncation), % (modulus), ** (exponentiation), +=, -=, *=, etc.

Strings:

• Quotes: Strings are created/delimit with Single quotes (') or Double quotes (")
• Modification: Strings can be concatenated using '+'
• Slicing: Strings can be sliced using '[start:end:step]'
• Splitting: Split strings using 'split()'
• Length: Get length using 'len()
• Single character: Get character using '[index]'
  print "Aardvark"[2]
  Output: r
  The [2] means to print the character at index 2 - Python counts from 0, so index 2 is the third character in the string.
  
• Special characters: Special characters escaped using '\', e.g. '\n' for newline.

Other operations: join, replace, duplicate, convert, and others.

Variables, Objects, References:

• Objects: Everything in Python is an object.
  x = 2
  y = x
  x = 4
  print y
  Output: 2
  When the 'y = x' is executed, the value of y is set to 2. Changing the value of x has no impact on the value of object y.
  
• Variables: Variable names are just references to an object.
  username = 'cisco'
  
• Assignment: Assignment means assigning a variable name to an object.
  new_username = username
  
• Modification: Reassignment of a variable name means it references a completely new object
  username = username + '123'

Code Blocks: Indentation:

• No 'begin' 'end', no '{' '}' to enclose code blocks.
• Blocks are identified by ':' and indentation:
  if a == b:
    # do something here
    # do more things
  else:
    # do else type things
• All code in code block must be indented identical numbers of spaces (no tabs please)
• Code block ends when indentation ends.

Commenting Your Code:

Importance of Comments:

Con: "Source code should be self-documenting"

Comments should:

• Explain why (the what is generally obvious)
• Be maintained and maintainable
• Be suitable for automatic document generation

Single-line comments:

• '#' denotes comment
• Quick explanation of non-intuitive code
• Explanation of this step in process
• Don't state the obvious

Multi-line comments:

• Triple quotes
  x = 1
  x = 2
  " " "
  x = 3
  x = 4
  " " "
  print x
  Output: 2
  First " " " begins a comment block, which is closed by the second " " ". x = 3 and x = 4 are not executed.
  
• At beginning of module
• At beginning of function
  
  • Purpose of function
  • Parameters
  • Return values
• Collected by document generation tool (pydoc)

PyDoc Auto / Automatically Program Documentation / Auto-Doc Generation / Generating:

In your code:

• Document module
• Document functions (purpose, parameters, return value)

Generate documentation:

• Run 'pydoc'
• Point it at source code
• Output is well-organized and structured documentation of your module
  Pydoc generates documentation from multiline comments in modules and functions in well-commented code.

Designing and Implementing Cisco Network Programmability:

• Minimizing the number of manual interactions with the network
• Reduce operational inefficiencies
• Improve productivity
• Create Scripts
• Create Code
• Work with sending and receiving information using commands sent via a web browser
• Linux
• Python - Relatively simple language
  
• What is an SDN? - Software Defined Network
• APIs
  
  • Enable a much more robust means of managing network devices than traditional methods
  • Native REST
  • NETCONF
  • RESTCONF
• XML
• JSON
• YANG
• SDN Controllers alleviate the problems by centralizing management of many devices in one single point of administration
• OpenFlow
• OPEN DAYLIGHT
• APIC-EM
• Efficiency
• Reliability
• Collaboration

Understanding Software-Defined Networking:

What is Software-Defined Networking?:

• An approach and architecture in networking where control and data planes are decoupled and intelligence and state are logically centralized.
• Enablement where underlying network infrastructure is abstracted from the applications [network virtualization].
• A concept that leverages programmatic interfaces to enable external systems to influence network provisioning, control, and operations.
• Is SDN one or more of these statements?

Software-Defined Networking is:

• An approach to network transformation
• Empowering external influencers to network design and operations
• Impacting the networking industry - challenging the way you think about engineering, implementing and managing networks
• Providing new methods to interact with equipment/services via controllers, APIs
• Normalizing the interface with equipment/services
• Enabling high-scale, rapid network and service provisioning/management
• Providing a catalyst for traditional Route/Switch engineers to branch-out
  

Network Programmability Technology:

• Linux
• Device and Controller APIs
• Version Control
• Software Development
• Automated Testing
• Continuous Integration
  
  
• GitHub
• git
• NX-API Developer Sandbox
• python
• Travis CI
  

Network Automation Workflow:

Configuration Management Workflow [Sample]:

• configs/fix_routing_policy
  - Review Config Changes ->
  <- git review ->
• Automated Testing
  Travis CI - merge ->
  tests:
  
  • Functional
  • Performance
  • Syntax
    
• Upstream (remote)
  Code/Config/Project
  configs/master
  git, GitHub - git clone ->
• Your Local Environment
  configs/master
  git branch fix_routing_policy
  configs/fix_routing_policy

Cisco Platforms and APIs:

• Platform(s)  | Programmatic API(s)
• IOS XE  | NETCONF, RESTCONF
• IOS XR  | NETCONF, RESTCONF, gRPC
• Nexus  | NX-API CLI, NX-API REST, NETCONF
• Adaptive Security Appliances (ASA)  | REST
• Application Centric Infrastructure (ACI) | REST
• APIC-EM  | REST
  
  
• Cisco platforms use NETCONF/RESTCONF and NX-API to provide network operators off-box programmability.

Linux Primer for Network Engineers:

Why Learn Linux?

Linux is everywhere - Used in various devices:

• Mobile devices
• Desktop Computers
• Production Servers
• Hypervisors
• Network switches

cisco@cisco: $ sudo su -
[sudo] password for cisco:
root@cisco: # exit
logout
cisco@cisco: $

• redhat
• debian
• CentOS
• fedora
• ubuntu

Though Linux is pervasive in technology, a network programmability engineer should learn Linux because:

• Network devices now expose the underlying Linux shell
• Network devices now enable engineers to run containers on the actual network device
• Most software development environments are Linux-based
• New open source projects such as Open vSwitch, Docker, and OpenStack all have a Linux foundation

Navigating the Linux File System:

Super User Privileges:

• The sudo command is short for "super user do"
• necessary to Run a program as other users (ex: root privileges by default)
• Can configure who can run sudo commands in the "sudoers" file
• Debian/Ubuntu distros do not enable the root user

Basic Commands:

• pwd  | Print working directory
• ls  | List contents of the working directory
• man <command> | View man pages (how-to) to learn how to use a given command and it's flags

Paths and Directories:

• Relative Path
  
  • Address relative to the current, or working, directory
• Absolute Path
  
  • Address relative to the root directory

cisco@cisco: /scripts$ pwd
/home/cisco/scripts
cisco@cisco: /scripts$ cd cisco
cisco@cisco: /scripts/cisco$ cd /var/log
cisco@cisco: /var/log$ pwd
/var/log

• Linux uses a single root file system which means all directories exist inside a single namespace referred to as /.
  

Change Directories:

• cd ..  | Change current directory to parent directory
• cd  | Back to the home directory
• cd ../.. | Back two directories (there is no limit on this)
• cd -  | Moves back to the previous working directory

Linux Distributions:

Debian:

• Free open source OS developed under the Debian Project
• Latest stable release is codenamed "stretch"
• Derivatives include Ubuntu and Mint (derivative of Ubuntu)

Red Hat Enterprise Linux:

• Red Hat's official commercial, distribution of Linux for training, services, and support
• RHL discontinued for RHEL
• Derivatives include Fedora and CentOS
  
  
• Kali Linux focused on penetration and security testing
• OpenWrt focused on home router functionality
  

Package Management:

• Packages are a convenient method to deliver software
• Package tool maintains a database of installed applications
• Two main CLI tools required to install, update and remove software

Red Hat Family:

• rpm  | Install local rpm package
• yum  | Download and install a package from repositories
• .rpm | File extension
  
  
• cisco@cisco: $ sudo yum install traceroute
• cisco@cisco: $ sudo rpm -i <package-name>.rpm

Debian Family:

• dpkg  | Command to install a local .deb package
• apt & apt-get | Commands to download and install packages
• .deb  | File extension
  
  
• cisco@cisco: $ sudo apt-get install traceroute
• cisco@cisco: $ sudo apt install traceroute
• cisco@cisco: $ sudo dpkg -i <package-name>.deb

Working with Files and Directories:

touch

• Updated timestamps of files and creates an "empty" file

cisco@cisco: $ touch catalyst_config.txt
cisco@cisco: $ ls
catalyst_config.txt  cisco  Desktop  Documents  Downloads  Templates
cisco@cisco: $ ls -l catalyst_config.txt
-rw-rw-r-- 1 cisco cisco 0 Jun 24 11:50 catalyst_config.txt

Make Directory Commands:

• mkdir  | Make a new directory
• mkdir -p | Make all required sub-directories in the path

Remove Commands:

• rm  | Removes a file
• rm -r  | Removes an entire directory and its contents
• rmdir  | Removes an entire empty directory
• rm -rf | Removes a directory and contents including write-protected files

Copy and Move Commands:

• cp  | Copy a file
• mv | Move/rename a file

cisco@cisco: /Nexus9000$ cp file1 file2
cisco@cisco: /Nexus9000$ mv file2 file3
cisco@cisco: /Nexus9000$ ls
file1 file3

cisco@cisco: $ mv class.txt MyClass is moving a file that is called class.txt from its current directory to a directory called MyClass.

Viewing Files Commands:

• more  | similar to using Cisco CL - space bar takes you down a full-screen length (% in the bottom left).
• less  | "less is more" because it allows the user to scroll up and down using arrow keys vs. just the ability to space down.
• cat  | Streams the file top to bottom without pausing.
• head | By default shows first 10 lines of a file.
• tail  | By default shows last 10 lines of a file.
• diff  | View diff between two files (hint: use -c option).

File Permissions:

Linux operating systems are multi-user

Permissions are based on two factors:

• Permissions assigned to a specific user and group
• Permissions assigned to a specific action (read, write, execute)

drwxrwxrwx:

• d - File Type
• First rwx - User
• Second rwx - Group
• Last rwx - Other

cisco@cisco: $ ls -l vlans_script.py
-rw-rw-r-- 1 cisco cisco 0 Sep 12 15:14 vlans_script.py
cisco@cisco: $ chmod u+x vlans_script.py
cisco@cisco: $ ls -l vlans_script.py
-rwxrw-r-- 1 cisco cisco 0 Sep 12 15:14 vlans_script.py
cisco@cisco: $ chmod go+x+w vlans_script.py
cisco@cisco: $ ls -l vlans_script.py
-rwxrwxrwx 1 cisco cisco 0 Sep 12 15:14 vlans_script.py

Data Types: Booleans:

• Values are True or False
• Operators are and, or, and not
• not takes the inverse
  
  

• Expressions evaluate to True or False
• Comparison Operators:
  
  • ==, !=, >, <, >=, <=
• Logical Operators:
  
  • and, or, not
• Membership Operators:
  
  • in, not in
• Identity Operators:
  
  • is, is not

>>> 9372 > 9396
False
>>> 'nexus' != 'catalyst'
True
>>> 'nexus' in 'nexus 9396'
True
>>> '9372' not in 'nexus 9396'
True

Conditional Statements:

• if, elif, else
  elif conditional statements is an optional condition that can be used numerous times to check for multiple expressions of True.
  
• End with a colon
• Consistent indentation required

>>> switch = 'catalyst 3850'
>>> if 'catalyst' in switch:
...   switch_type = 'catalyst'
... elif 'nexus' in switch:
...   switch_type = 'nexus'
... else:
...   switch_type = 'unknown'
...
>>> print switch_type
catalyst

Summary:

Create Strings:

• >>> ipaddr = '10.1.1.1'
  >>> print ipaddr
  10.1.1.1
  
  
• >>> mask = '255.255.255.0'
  >>> print mask
  255.255.255.0
  
  
• >>> hostname = 'router_1'
  >>> print hostname
  router_1
  
  
• >>> os_version = '15.4'
  >>> print os_version
  15.4
  
  
• >>> switch = 'NEXUS'
  >>> print switch
  NEXUS
  
  
• >>> ipmask = ipaddr + ' ' + mask
  >>> print ipmask
  10.1.1.1 255.255.255.0

Navigate the Built-In Help Features:

• >>> campus_switch = 'catalyst'
  >>> print campus_switch
  catalyst
  
  
• >>> type(campus_switch)
  <type 'str'>
  
  
• >>> dir(campus_switch)
  ...
  ['rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', ...,
  'swapcase', 'title', 'translate', 'upper', 'zfill']
  
  
• >>> help(campus_switch.upper)
  Help on built-in function upper:
  
  upper(...)
      S.upper() -> string
  
      Return a copy of the string S converted to uppercase.
  
  >>> help(campus_switch.startswith)
  Help on built-in function startswith:
  
  startswith(...)
      S.startswith(prefix[, start[, end]]) -> bool
  
      Return True if S starts with the specified prefix, False otherwise.
      With optional start, test S beginning at that position.
      With optional end, stop comparing S at that position.
      the prefix can also be a tuple of strings to try.

Use Built-in Methods of Strings:

• >>> 'nxos1'.upper()
  'NXOS1'
  
  
• >>> description = "The device type is an {}"
  >>> description.format('ASR')
  'The device type is an ASR'
  
  
• >>> ip = '10.1.1.1'
  >>> ip.startswith('100')
  False
  
  
• >>> ip.split('.')[0]
  '10'
  >>> ip.split('.')[3]
  '1'
  
  
• The associated return data type:
  
  • upper() and string
  • startswith() and boolean
  • split() and list
    
    
• >>> 'Eth1'.lower().startswith('et')
  True
  >>> 'Eth1'.startswith('et')
  False
  

Use Conditionals:

• >>> router = 'asr_1006'
  >>> print router
  asr_1006
  
  
• >>> if router.startswith('asr'):
  ...   router_type = 'asr'
  ... elif router.startswith('isr'):
  ...   router_type = 'isr'
  ... else:
  ...   router_type = 'unknown'
  ...
  >>> print router_type
  asr
  
  
• >>> router = 'nexus9k'
  >>> if router.startswith('asr'):
  ...   router_type = 'asr'
  ... elif router.startswith('isr'):
  ...   router_type = 'isr'
  ... else:
  ...   router_type = 'unknown'
  ...
  >>> print router_type
  unknown

Programming the Digital Network Architecture (DNA):

Programming Foundation:

Coding 101 - REST API Basics with APIC-EM:

What is a Web Service?

• A web service is a way for two systems to communicate through a defined interface.
• There are two major types of web services - REST and SOAP.

What is a REST Web Service?

• REST is an architecture style for designing networked applications.
• A REST web service is as easy to call as making an HTTP request.
• RESTful interfaces usually offer the CRUD (Create, Update, Delete) operations.
• To know more about REST in general, this is a great REST tutorial: rest.elkstein.org

What are the benefits of REST?

REST Is easy to use on any platform

• The Application Policy Infrastructure Control (APIC) Enterprise Module (EM), Application Programming Interface (API), APIC-EM APIs, enables deploying and running application policies across networking infrastructure.
  
  
• Using the APIC-EM APIs, can retrieve information about devices on network including a list of hosts, network devices, or users.
  
  
• Look at the APIC-EM Reference Docs: devnetapic.cisco.com to see the details of the APIC-EM functions.

How does this work?

• REST is centered around the HTTP request and response model. Consuming an API is as simple as making an HTTP request.
  
  
• In this example, request the list of hosts, and that information is returned in the response. The data returned in the response is usually formatted as JSON or XML.
  (JSON -- JavaScript Object Notation, is a lightweight text-based open standard designed for human-readable data interchange.)

What do I need to know to make a Request?

To construct a request, determine the following information for the API that are calling. Can find this information in the API reference documentation.

• Method:
  Choose one of the following http methods:
  
  • GET - Retrieve data
  • POST - Create something new
  • PUT - Update data
  • DELETE - Delete data
    
    
• URL:
  
  • Determine the URL of the endpoint want to call.
  • Example: http://{APIC-EMController}/api/v1/ticket
    
    • Where {APIC-EMController} is the controller IP or hostname.
  • Enter the URL/IP address of an APIC-EM controller on network.
    
    
• URL Parameters:
  
  • If the endpoint requires URL parameters, pass them as part of the URL. To get this information, refer to the reference documentation for the particular endpoint.
    

• Designed for the Internet
• Schema or namespace defines data model
• <tags></tags> surround elements for structure and layout
• Key/Value representation:
  
  • <key>value</key>
• Whitespace not significant

XML Object:

• A related set of data surrounded by <tags></tags>
• An object can contain other objects or data entries
• <key>value</key> contained within the object tags

XML List:

• List of data:
  
  • Can be composed of XML objects
• Repeated instances of <tags></tags> for each element
  
  
• <?xml version="1.0" encoding="UTF-8" ?>
  <addresses>
    <ip>172.16.0.2</ip>
    <netmask>255.255.255.0</netmask>
  </addresses>
  <addresses>
    <ip>172.16.0.3</ip>
    <netmask>255.255.255.0</netmask>
  </addresses>
  

Breakdown JSON: JSON - JavaScript Object Notation:

• A data-interchange text format
• Notated with { } for objects, [ ] for arrays
• Key/Value representation:
  
  • "key": value
• Whitespace not significant

JSON Object:

• Data surrounded by { }
• An object can contain other objects or data entries
• Key/Value set separated by comma
• No comma at the end!

JSON List:

• List of data
  
  • Can be composed of JSON objects
• Notated with brackets
• Comma Separated
  
  
• {
    "addresses": [
      {
        "ip": "172.16.0.2",
        "netmask": "255.255.255.0"
      },
      {
        "ip": "172.16.0.3",
        "netmask": "255.255.255.0"
      }
    ]
  }
  

Simplify YAML: YAML - "YAML Ain't Markup Language":

• Minimalist format commonly used for configuration files
• Whitespace indentation defines structure
  
  • No commas
• Key/Value representation
  
  • key: value

YAML Object:

• Related set of data at the common indentation level under name
• An object can contain other objects or data entries
• key: value pairs left aligned

YAML List:

• List of data:
  
  • Can be composed of YAML objects
• Uses "-" character to indicate a list element
  
  
• ---
  addresses:
  - ip: 172.16.0.2
    netmask: 255.255.255.0
  - ip: 172.16.0.3
    netmask: 255.255.255.0

APIs are Everywhere... but what are they?:

What is an API?:

"It's a way for two pieces of software to talk to each other"

Application Programming Interface (API)

For a long time... Humans were the only users:

• Software displays results in User Interface (UI)
• User asks for data or takes action by interacting with UI

But what about when the user is another software system...:

• Your Software System - Software returns results via API >
  
• My Software System - Software asks for data or takes action by interacting with API >

The API is the User Interface for software systems

APIs are sets of requirements that govern how one application can talk to another.

An API is like an electrical outlet:

What would it be like to power a hair dryer without an outlet?:

• Open wall
• Strip Wires
• Splice wires together
• Understand all the wires on the wall

The outlet is a service that conforms to specifications:

• Sockets deliver 120 volts of alternating current (AC) operating at 60Hz
• Sets expectation on behalf of consumer devices and provider

An API is like ...:

An API (Application Programming Interface) is best thought of as a contract provided by one piece of computer software to another.

APIs help developers create apps that benefit the end user:

- Yelp asks for Map Data > Google Maps - returns map data via API > yelp > Users sees list of restaurants close to them

APIs are often referred to as "an engine of innovation." -- Programmable Web

APIs aren't scary... you already use them:

Command Line Interface (CLI):

Designed for Humans... so more a UI than API but ...:

• Network Management Systems
• Expect Scripts
• Paramiko/Netmiko
• NAPALM
  
  
• #!/usr/bin/expect -f
  
  send "conf t\n"
  expect "(config)#"
  
  send "hostname my_switch\n"
  expect "(config)#"
  send "ntp server 10.10.10.101\n"
  expect "(config)#"
  send "ip domain-name domain.intra\n"
  expect "(config)#"
  
  send "end\n"
  expect "#"
  send "write mem\n"
  expect "#"

Simple Network Management Protocol (SNMP):

• "designed as a programmatic interface between management applications and devices"
  tools.ietf.org/html/rfc3535
• Widely used for monitoring
• Limited use for configuration
• Network Management Systems primary consumer

Other APIs out there:

Simple Object Access Protocol (SOAP):

• Mature standard designed by Microsoft
• Used to build "Web Services" (software available over the internet)
• Typically uses HTTP, and dependent on XML
• Sometimes considered complex and rigid
  
  
• SOAP Web Service Communications:
  Messaging Client < HTTP : SOAP Implementation : SOAP Message > SOAP Service

Representational State Transfer (REST):

• API framework intended to build simpler web services than SOAP
• Another use for the HTTP protocol
• Popular due to performance, scale, simplicity, and reliability
• Technically an API framework
  
  
• GET, POST, PUT, DELETE

XML-RPC and JSON-RPC:

• Simple frameworks for communicating over HTTP
• RPC = Remote Procedure Call
  
  • When one system requests another system to execute code
• Offer XML and JSON data formats respectively
  
  
• HTTP POST
  REQUEST BODY:
  [
    {
      "jsonrpc": "2.0",
      "method": "cli",
      "params":
      {
        "cmd": "show version",
        "version": 1
      },
      "id": 1
    }
  ]

NETCONF (NETwork CONFiguration) Protocol:

• Designed as replacement for SNMP
• Standardized in 2006 / Updated 2011
• Leverages SSH and XML
• Defines transport and communication
  
  • Titled coupled to YANG for data
    
    
• NETCONF Communications:
  Manager < NETCONF : XML : YANG Data > Agent
  
  
• XML:
  
  • Content  | Configuration / Operational Data  | <data>
  • Operations | Actions to Take  | <get>, <get-config>, <edit-config>, etc
  • Messages  | Remote Procedure Call (RPC) | <rpc>, <rpc-reply>
• Transport | TCP/IP Method | SSH

RESTCONF Protocol:

• Provide REST API like interface to network
• Standardized in 2017
• Supports XML and JSON
• Defines transport and communication
  
  • Titled coupled to YANG for data
    
    
• Content  | Configuration / Operational Data  | XML or JSON
  
• Operations | Actions to Take  | GET, POST, PUT, PATCH, DELETE
  
• Transport  | TCP/IP Method  | HTTP
  

API Collections:

• Save and Organize API Calls into Collections

Using Environments:

Variables Make Requests Reusable and Flexible:

• Never good to hardcode details
• What if you want to connect to different host?
• What if credentials change?

Variables Make Requests Reusable and Flexible:

• Variables References:
  
  • {{apic}}
  • {{username}}
  • {{password}}

Managing Environments:

• Create any number of environments needed
• Change between environments with a drop-down list
• Add as many variables as needed
• Reference anywhere with {{variable name}} syntax

Setting Environment Variables Dynamically:

• What about when info from one request is needed in another?
• Manually copying/pasting slow and error-prone
• Manually updating environment variables is slow and awkward
  
  
• Login Response:
  {
    "response": {
      "serviceTicket": "ST-6862-5DmKf5FrP0S4bSjy9rDM-cas",
      "idleTimeout": 1800,
      "sessionTimeout": 21600
    },
    "version": "1.0"
  }
  
  
• Device List Request:
  > Network Device List
  

"Tests" Enable Dynamic Environment Variables:

• Each API Request offers both pre and post actions:
  
  • Pre -> Pre-request Script
  • Post -> Tests
• Written in JavaScript
  
  
• var jsonData = JSON.parse(responseBody);
  postman.setEnvironmentVariable("token",
    jsonData.response.serviceTicket);
  
  

Postman to Code!:

You'll eventually want to write some code...:

• Postman great for testing and validating APIs
• But it's about atomic actions
• Business Logic, stringing APIs together, etc all need code
• Jumpstart with auto-generated code by Postman
• Many, many options for languages available

Full API Request to Code!:

• Headers, payload data, and URI all included
• Environment variables are translated
• A great starting point, but expect to edit and update
  
  

Python Language and Script Basics:

Why Python and How to get it?:

• Python is powerful... and fast;
  plays well with others;
  runs everywhere;
  is friendly & easy to learn;
  is Open.
  www.python.org/about

The Zen of Python by Tim Peters:

• Simple is better than complex.
  
• The complex is better than complicated.
  
• Special cases aren't special enough to break the rules.
  
• Now is better than never.
  
• Although never is often better than *right* now.
  
• If the implementation is hard to explain, it's a bad idea.
  
  
• Beautiful is better than ugly.
  
• Explicit is better than implicit.
  
• A flat is better than nested.
  
• Sparse is better than dense.
  
• Readability counts.
  
• Although practicality beats purity.
  
• Errors should never pass silently.
  
• Unless explicitly silenced.
  
• In the face of ambiguity, refuse the temptation to guess.
  
• There should be one-- and preferably only one --obvious way to do it.
  
• Although that way may not be obvious at first unless you're Dutch.
  
• If the implementation is easy to explain, it may be a good idea.
  
• Namespaces are one honking great idea -- let's do more of those!

Why Python for Network Engineers:

• Readable and easy to learn
• Widely available and Open Source
  
  • Windows, Mac, Linux
  • Routers & Switches
• Many relevant code samples
• Lots of training resources

How to get Python?

• Might already have it
• python.org/downloads
• Package Management Tools
  
  • Example: Homebrew for Mac
    
    • brew install python2
    • brew install python3

  DevNet$ python -version
  Python 2.7.12

Breaking Down Python Code:

example1.py:

• Script Structure and Format
• Importing and using packages
• Variable declaration and usage
• Function creations and usage
• Basic Error Handling
  
  
• # Entry point for program
  if _name_ == '_main_':
      # Retrieve command line input
      try:
          input = float(sys.argv[1])
      except (IndexError, ValueError) as e:
          # Indicates no command line parameter was provided
          print("You must provide a number as a parameter to this script")
          print("Example: ")
          print(" python example1.py 12")
          sys.exit(1)
         
      # Double the provided number and print output
      answer = doubler(input)
      print(answer)
  
  
• In JSON in the payload are authentication credentials sent in a Cisco APIC REST API authorization request.
  www.cisco.com/c/en/us/td/docs/switches/datacenter/aci/apic/sw/2-x/rest_cfg/2_1_x/b_Cisco_APIC_REST_API_Configuration_Guide.html
  
  
• OpenFlow automatically determines network forwarding rules and OpenFlow interfaces with the management plane.

Fundamentals of Open SDN and OpenFlow:

What is "Open?":

• Open Standards:
  
  • BGP, VLAN, VxLAN
  • OpenFlow, I2RS, NetConf, YANG, OpFlex
• Open Source Software:
  
  • OpenStack, OVS, OpenDaylight
  • Neutron
• APIs and SDKs
• Open Hardware:
  
  • Open Compute Project
    
    
• cloudstack - Open Source Cloud Computing project
• ETSI - ETSI SGI on "Network Function Virtualization"
• IEEE - 802.1 Overlay Networking Projects
• IETF:
  
  • Overlay Working Groups:
    NVO3, L2VPN, TRILL, L3VPN, LISP, PWE3
  • API Working Groups/BOFs:
    NETCONF, ALTO, CDNI, XMPP, SDNP, I2AEX
  • Controller Working Groups:
    PCE, FORCES
  • New working group:
    I2RS - Interface to the Routing System
• IRTF - SDN WG
• ITU
• ONF (Open Networking Foundation) - Technical Advisory Group, Working Groups: Config, Hybrid, Extensibility, Futures/FPMOD/OF2.0
• ONRC (Open Network Research Center) at Stanford University
  
• Open Daylight: ODL Controller
• OpenStack: Neutron (a.k.a. Quantum)
  
• MEF
• W3C

SDN Protocols: > Application Frameworks, Management Systems, Controllers, ...

• Device:
  
  • Operating Systems - Cisco IOS / NX-OS / IOS-XR
  • BGP Diameter Radius SNMP ...
  • Cisco API & Agent Infrastructure (Chef, Puppet, YANG, etc.) > onePK > NETCONF
    
• Forwarding:
  
  • BGP Diameter Radius SNMP ...
  • OpenFlow - ONF
    
• Control:
  
  • BGP Diameter Radius SNMP ...
  • I2RS - IETF
    
• Network Services:
  
  • BGP Diameter Radius SNMP ... > "Protocols"
    
  • PCEP - IETF
  • BGP-LS/FS - IETF
• Orchestration:
  
  • OpenStack > Neutron
• Management:
  
  • OMI
  • Puppet
  • NETCONF - IETF
  • ...
    

Evolving Our Interaction with Network OS:

• Types of Interactions:
  
  • Bootstrap
  • Configure
  • Monitoring
  • Extend
• What's Evolving:
  
  • Manual > Automated
  • Static > Dynamic
  • Generic > Custom
• Why?:
  
  • Agility
  • Scale
  • Cost
  • Complexity

How > 70% of Config Management is Done Today:

"It's the way real men build real networks."

• Software Unfriendly
• Subject To Change
• No Common Data Model
• No Error Reporting
  
  
• Task Oriented
• Human-Friendly
• Easy To Replay
• No Special Tools

Ways to Automate Network Components:

• On / Off Box:
  #!/usr/bin/env python
  print('Hello World!')
• via SDN Controller

Programmability - SDN:

• Northbound Programmability Layer:
  
  • Automation: CFEngine, python, puppet, CC Opscode
  • Hypervisor Management: Redhat, Oracle, Xen, VMware, Windows
  • Enterprise Monitoring: Tivoli, Splunk, netscout
  • System Management: IBM, ca, bmc, hp
  • Orchestration Frameworks: Redhat, cloupia, OpenStack, VMware, cloudstack
  • Application: SAP, MapR, Cloudera
• REST API / SDK / Plugins
• SDN Control Plane: VTS, APIC, APIC-EM, ODL
• Southbound Programmability Layer:
  
  • OpFlex
  • Netconf YANG
  • CLI
  • NX-API
  • BGP-EVPN
  • OpenFlow
    
    
  • Virtualized Environment: OVS / VTF / AVS
  • Switch / Nexus 9K / Routers

Options for Programming the DC Network:

• Programmable Network: Traditional 2/3-Tier:
  
  • Modernized Operating System
  • Programmable Open APIs
  • HW & SW Disaggregation
• Programmable Fabric: Open Controller Model:
  
  • L2 / L3 Overlay & Underlay
  • Physical & Virtual Endpoints
  • Decoupled Controllers
  • VXLAN Overlay
• Integrated Fabric: Cisco APIC:
  
  • Any Hypervisor
  • Physical. Virtual / Open API's
  • Day 1 & 2 Ops
  • Gartner: ACI outpacing competitors by 2x to 5x

Requirements of Next-Gen Config Management: RFC 3535 CY 2002:

• Easy to Use
• Separates Config and Operational Data
• The configuration of Network as a whole
• Common database schema
• Error Checking
• Backup/Restore Capability
• Human & Machine Friendly

Result: NETCONF and YANG:

• NETCONF:
  
  • IETF standard - RFC 6241
  • Designed for network programmability
  • Session and connection-oriented
  • Runs over SSH or SOAP
• YANG:
  
  • IETF standard - RFC 6020, 6021
  • Data Modeling language for networking (config & state)
  • Explicitly & precisely defines the structure, syntax & semantics of data
  • Represents data structures in XML tree format
• RESTCONF:
  
  • IETF draft
  • Designed for web applications (REST "like", based on NETCONF)
  • Access data defined in YANG using datastores defined in NETCONF
  • Runs over HTTP/S

NETCONF (Network Configuration Protocol): NETCONF 1.1:

• RFC 6241 - Base NETCONF 1.1 Protocol (1.0 defined in RFC 4741)
• RFC 6242 - NETCONF over SSH, port 830/tcp (1.0 transport defined in RFC 4742)
• Extensions: RFC 5277 Notifications, RFC 5717 Partial Locking, RFC 6243 With defaults
• Informational: RFC 3535 Background and Requirements, RFC 6244 NC/Yang Architecture
  
  
• IETF protocol for configuration data and operational state data management & notifications
• Addresses SNMP SMI short-comings like no transactions, no backup&restore, strange&legacy concepts...
• Based on XML (Yang to provide the data modelling)
• 830/tcp - runs over SSH (possibly also TLS, BEEP...)
  
  Client <-> Server:
  
• Content: Config and Oper data, Notifications (XML format, modelled in YANG)
• Operations: <get>, <get-config>, <edit-config>...
• Messages: <rpc>, <rpc-reply>
• Transport: SSH
  
  
• <?xml version="1.0" encoding="UTF-8"?>
  <rpc message-id="101"
    xmlns="urn:ietf:params:xml:ns:netconf:base:1.0">
    <get-config>
      <source>
        <running/>
      </source>
      <filter
        xmlns: if="urn:ietf:params:xml:ns:yang:ietf-interfaces"
        type="xpath"
        select="/if:interfaces/if:interface[if:name='eth0']"/>
    </get-config>
  </rpc>
  ]]>]]>
  
  
• Huawei SDN solution:
  
  
  
  • Agile Controller for TE configuration
  • AC Super for services configuration
    
  
  
• Configuring NETCONF-Over-SSH Connections on a Specified TCP Port:
  www.juniper.net/documentation/en_US/junos/topics/task/configuration/netconf-over-ssh-connections-port-configuring.html
  
  
• JSON-RPC is a remote procedure call (RPC) protocol built on JSON, as a replacement for XML-RPC or SOAP. It is a simple protocol that defines only a handful of data types and commands. JSON-RPC lets a system send notifications (information to the server that does not require a response) and multiple calls to the server that can be answered out of order. Example of a JSON-RPC 2.0 request and response using positional parameters.
  en.wikipedia.org/wiki/JSON#JSON-RPC
  
  
• Develop an open-source package or SDK and Use the API inspector and test API calls are two initial actions should take when exploring automation for ACI.
  
  
• YANG comments are C++ style. A single line comment starts with "//" and ends at the end of the line. A block comment is enclosed within "/*" and "*/".
  tools.ietf.org/html/draft-ietf-netmod-yang-00#section-6.1.1
  
  
• 3 Cisco APIs must fail, in order for a customer running an ACI fabric with a cluster of five APICs to experience data loss.
  www.cisco.com/c/en/us/solutions/collateral/data-center-virtualization/unified-fabric/white-paper-c11-730021.html
  
  
• Network automation protocol > Transport protocol that it supports:
  
  • RESTCONF > HTTP
  • gRPC  > HTTP/2
  • NETCONF  > SSH
    
    
• Adding the managed hosts to Management Server using an agentless configuration:
  sort.symantec.com/public/documents/vom/6.1/windowsandunix/productguides/html/Install_Config_Guide/ch07s04.htm
  
  
• An organization leverages a multivendor network to sell connectivity services using Layer 3 VPN and VPLS. Where possible, the organization wants to use common APIs across vendors, in order to automate the configuration of network services. The organization should consider NETCONF technology for the southbound interface.
  
  translate.google.co.th/translate?hl=en&sl=zh-CN&u=https://blog.csdn.net/zengxiaosen/article/details/73500838
  
  
• YANG State Data:
  tools.ietf.org/html/rfc6020#section-4.2.3
  
  
• What is SDN Southbound APIs?:
  www.sdxcentral.com/sdn/definitions/southbound-interface-api
  
  
• SNMP, NETCONF, RESTCONF, gRPC:
  
  
  www.slideshare.net/roy1022/netconf-restconf-grpcbasic
  
  
• NETCONF, YANG, RESTCONF - TECH-SDN-SP: Software Defined Networking for Service Providers:
  www.cisco.com/c/dam/global/cs_cz/assets/ciscoconnect/2014/assets/tech_sdn10_sp_netconf_yang_restconf_martinkramolis.pdf