Testbed-Topology

Testbed

Generate from Excel/CSV file

• Generating from excel or csv file: pyats|genie create testbed file --path source.xls --output testbed/DC.yml

  • Option --encode-password will obfuscate the password. For better security, use secret string

• https://pubhub.devnetcloud.com/media/genie-docs/docs/cli/genie_create.html

• https://pubhub.devnetcloud.com/media/pyats-getting-started/docs/quickstart/manageconnections.html

# source.xls
hostname,ip,username,password,protocol,os
R1,10.10.10.1:222,admin,cisco,ssh,iosxe
R2,10.10.10.2:222,admin,,ssh,iosxr
R3,10.10.10.3:222,admin,,ssh,nxos

• Sample generated testbed file, which can be manually created as well:

devices:
  R1:
    connections:
      cli:
        ip: 10.10.10.1
        port: 222
        protocol: ssh
    credentials:
      default:
        password: cisco
        username: admin
      enable:
        password: cisco
    os: iosxe
    type: iosxe
  R2:
    connections:
      cli:
        ip: 10.10.10.2
        port: 222
        protocol: ssh
    credentials:
      default:
        password: '%ASK{}'
        username: admin
      enable:
        password: '%ASK{}'
    os: iosxr
    type: iosxr
  R3:
    connections:
      cli:
        ip: 10.10.10.3
        port: 222
        protocol: ssh
    credentials:
      default:
        password: '%ASK{}'
        username: admin
      enable:
        password: '%ASK{}'
    os: nxos
    type: nxos

Generate testbed interactively

• pyats create testbed interactive --output mytb.yaml --encode-password

Generate testbed from Python Dictionary

• Create testbed from a dictionary

Validate Testbed file

• pyats validate testbed $file

• Validate testbed

Secret Strings

• Secret strings (such as passwords) may be specified in an encoded form suitable for sharing with a wide audience, while ensuring that only authorized users are able to decode these strings into their plaintext form.

• By default, pyATS secret strings are not cryptographically secure.

• https://pubhub.devnetcloud.com/media/pyats/docs/utilities/secret_strings.html

Secure secret strings cryptographically

1. Update Configuration file:

[secrets]
string.representer = pyats.utils.secret_strings.FernetSecretStringRepresenter

1. Install the cryptography package: pip install cryptography

2. Ensure permission to access configuration file is set correctly: chmod 600 ~/.pyats/pyats.conf

3. Generate a cryptography key: pyats secret keygen

4. Update configuration file

[secrets]
string.representer = pyats.utils.secret_strings.FernetSecretStringRepresenter
string.key = $GeneratedKeyFromStep4

1. Encode a password

> pyats secret encode [--prefix my_custom]
Password: MySecretPassword
Encoded string :
gAAAAABdsgvwElU9_3RTZsRnd4b1l3Es2gV6Y_DUnUE8C9y3SdZGBc2v0B2m9sKVz80jyeYhlWKMDwtqfwlbg4sQ2Y0a843luOrZyyOuCgZ7bxE5X3Dk_NY=

OR

> pyats secret encode --string MySecretPassword [--prefix my_custom]
Encoded string :
gAAAAABdsgvwElU9_3RTZsRnd4b1l3Es2gV6Y_DUnUE8C9y3SdZGBc2v0B2m9sKVz80jyeYhlWKMDwtqfwlbg4sQ2Y0a843luOrZyyOuCgZ7bxE5X3Dk_NY=

1. Decode encoded password

> pyats secret decode gAAAAABdsgvwElU9_3RTZsRnd4b1l3Es2gV6Y_DUnUE8C9y3SdZGBc2v0B2m9sKVz80jyeYhlWKMDwtqfwlbg4sQ2Y0a843luOrZyyOuCgZ7bxE5X3Dk_NY=
Decoded string :
MySecretPassword

1. Add encrypted password to testbed

# Snippet of your testbed.yaml
testbed:
    name: sampleTestbed
    credentials:
        default:
            username: admin
            password: "%ENC{gAAAAABdsgvwElU9_3RTZsRnd4b1l3Es2gV6Y_DUnUE8C9y3SdZGBc2v0B2m9sKVz80jyeYhlWKMDwtqfwlbg4sQ2Y0a843luOrZyyOuCgZ7bxE5X3Dk_NY=}"

# With prefix
testbed:
    credentials:
        default:
            username: my_username
            password: "%ENC{wr3DssK0w5nDlsORw4nDmcK2w4LDqMOfw6vDjsOdw4k=}"
        alternate:
            username: alternate_username
            password: "%ENC{<my_custom encoded string>, prefix=my_custom}"
    custom:
        custom_key: |4-
            custom data containing encoded text
            %ENC{<my_custom encoded string>, prefix=my_custom}

1. Check that passwords can be recovered from loaded testbed

> pyats shell --testbed_file my_testbed.yaml
>>> from pyats.utils.secret_strings import to_plaintext
>>> to_plaintext(testbed.credentials.default.password)
'MySecretPassword'
>>> to_plaintext(testbed.credentials.alternate.password)
'MySecretPassword'
>>> testbed.custom.custom_key
'custom data containing encoded text\nMySecretPassword'

Using Secret String Object

from pyats.utils.secret_strings import to_plaintext, SecretString

# Create a secret string by specifying its encoded form.
# The ``pyats secret encode`` CLI command may be used to convert a
# plaintext string to encoded form.
my_secret = SecretString('w53DssKBw6fDmMOCw5bDisOa')

# Decode the password
my_secret.plaintext
'my password'

# Create a secret string from plaintext.
my_secret =  SecretString.from_plaintext('another secret')

# Asterisks are shown when the secret is printed.
print(my_secret)
**************

# Print the secret string in plaintext form.
# The ``pyats secret decode`` CLI command may be used to convert
# an encoded string to plaintext form.
to_plaintext(my_secret)
'another secret'

# to_plaintext works on regular strings as well.
to_plaintext('plain string')
'plain string'

# Print the secret string in its encoded form.
my_secret.data
'w53DssKBw6fDmMOCw5bDisOa'

# Allocate a brand new key.
# This does the same thing as the ``pyats secret keygen`` CLI command.
print(SecretString.keygen())

# Allocate a secret string that stores a string in plaintext (non-encoded)
# form.
from pyats.utils.secret_strings import PlainTextSecretStringRepresenter
weak_secret = SecretString('weak_pw', representer_cls= PlainTextSecretStringRepresenter)

Customizing Connection

• Allow users to tune unicon plugin behavior without the need for any code changes, several kinds of overrides may be made from the testbed YAML itself.

• Connecting to a pyATS device via unicon ultimately results in a unicon Connection object being created. The following parameters are eligible for override under the arguments key in the testbed YAML connection block:

  • learn_hostname

  • prompt_recovery

  • init_exec_commands

  • init_config_commands

  • mit

  • log_stdout

  • debug

  • goto_enable

  • standby_goto_enable

• Customizing your connection

• By default, after logging in device, pyats will change terminal settings both in terminal and in config mode and also show output to stdout. To disable, used below config

device.connect(init_exec_commands=[],
               init_config_commands=[],
               log_stdout=False)

Error Pattern Handling

• c.execute('show interface invalid', error_pattern=['^% Invalid'])

from pyats.topology import loader

tb = loader.load('testbed.yaml')
ncs = tb.devices.ncs

ncs.connect(via='cli')
ncs.settings.ERROR_PATTERN=[]

• Default error patterns:

ncs.settings.ERROR_PATTERN
['Error:', 'syntax error', 'Aborted', 'result false']

• Pass an empty list to avoide error pattern checking: c.execute('show command error', error_pattern=[])

Set Environment Variables for connection

• uut.settings.ENV = {'MYENV': 'mystring'}

Set Terminal Size Settings

• uut.settings.ENV = {'ROWS': 200, 'COLUMNS': 200}

Logging

• Every unicon device connection Logger has 3 handlers.

1. Screen Handler: This logs messages on stdout

2. File Handler: This logs messages in file /tmp/--.log. This is default log file. To modify the file value, the logfile parameter can be used.

3. pyATS TaskLog Handler: This logs messages in pyats TaskLog file

• Log level of device output and service messages is INFO.

Change logfile when connecting

• In unicon standalone mode:

dev = Connection(hostname=uut_hostname,
                   start=[uut_start_cmd],
                   logfile='user-provided-file')

• With pyATS: dev.connect(logfile='user-provided-file')

Disable unicon device connection logging

• Set logger level above logging.INFO.

import logging
uut.log.setLevel(logging.WARNING)

# To enable debug logs, use below:
import logging
uut.log.setLevel(logging.DEBUG)

# in Testbed file
devices:
  PE1:
    connections:
      defaults:
        class: 'unicon.Unicon'
        debug: True

# With pyATS
dev.connect(log_stdout=False)

Topology

• Topology module is delivered as part of base pyATS installation in the form of a Python Package

• Installation if needed: pip install pyats.topology

Device Object

• Device objects represent any piece of physical and/or virtual hardware that constitutes an important part of a testbed topology.

  • Each device may belong to a testbed (added to a Testbed object)

  • Each device may host arbitrary number of interfaces (Interface objects)

  • Interface names must be unique within a device

Creating Topology

There are two ways to create a topology within your testscript:

1. create each testbed object from topology module classes and craft their interconnects together manually (eg, by assigning interfaces to each device).

2. create a YAML testbed description file, and load it using the topology loader function.

Reference

• Getting Started

• https://developer.cisco.com/netdevops/live

• https://developer.cisco.com/pyats/

• PyATS Hands on Learning

• https://github.com/CiscoTestAutomation?utm_campaign=oyoutube-davidbombal&utm_source=oyoutube&utm_medium=davidbombal-video13

• https://github.com/hpreston/netdevops_demos

• Genie makes all your network automation wishes come true (most of them)! Hank Preston explains: https://www.youtube.com/watch?v=unOmwDsMj8k

• pyATS Series - Parsing like a pro: https://xrdocs.io/programmability/tutorials/pyats-series-parsing-like-a-pro/

• Parse Genie: https://developer.cisco.com/codeexchange/github/repo/clay584/parse_genie/

• pyATS Tutorial for Beginners: https://www.rogerperkin.co.uk/network-automation/pyats/pyats-genie-tutorial/

• Explore Genie: https://pubhub.devnetcloud.com/media/genie-docs/docs/cookbooks/explore.html

• https://pubhub.devnetcloud.com/media/genie-docs/docs/overview/introduction.html

• Intro Network Test

• Testbed & Topology Information

• Useful Libraries

• Learn Device Features

• First Steps with PyATS

• Cisco Test Automation github

• Automated testing using PyATS and Genie