Netmiko Sandbox

What is it?

This is an implementation of a Fake Device to create development sandbox to allow network engineers and developers to work with different vendor device types in a netmiko-like style, to retrieve raw or structured command outputs, without the requirement of running physical or virtual devices.

How does it work?

NetmikoMock overwrites netmiko methods used to make connection to a device to retrieve command outputs. It's coupled with ntc-templates repository (sub-repository) which has many textFSM templates and mocked data for tests containing many raw & structured command outputs from multiple devices of different vendors. This fake device leverages these mock files to return command output like netmiko does, but this time without the need of running real or virtual devices.

Key features

It reads textFSM CliTable index file available in ntc-templates directory, so it's able to "auto-complete" commands.

Caveats

When a directory with mocked files for a specific textFSM template is detected the first .raw or .yml file is returned, depending on requested type (raw or structured). When many mock files are present under mock files, always the first one is returned.

Supported commands are limited to those having textFSM template and mock files in ntc-templates repository.

Use Cases

• Easy access to command outputs from many devices of different vendor types.
• Facilitate local development of netmiko scripts when device(s) are not available.
• Facilitate collecting raw or structured command outputs when developing network tests and mocking netmiko responses.

Cloning repositories

git clone https://github.com/pszulczewski/netmiko_sandbox.git
cd netmiko_sandbox
# clone ntc-templates as sub-repository
git clone https://github.com/networktocode/ntc-templates.git

Create environment

poetry install

poetry shell and you're good to go!

Developing netmiko scripts with NetmikoMock

Connecting do devices over and over when developing scripts can be slow, you can greatly speed it up by using Mock in similar way as using mocks for tests.

Let's consider two potential scenarios:

1. import NetmikoMock as ConnectHandler the same way as you usually import ConnectHandler from netmiko and then work on your development locally. You can switch back to netmiko just by removing that extra import statement whenever you're ready to use your script on real devices.
2. Use NetmikoMock for a device or group of devices which you can't connect to.

See main.py for some examples. Keep in mind that commands are limited to what's available in ntc-templates repository.

Using CLI tool to collect command outputs when mocking device responses.

$ ./cli.py -h
usage: cli.py [-h] -d DEVICE_TYPE -c COMMAND [-u] [-p] [-j]

optional arguments:
  -h, --help            show this help message and exit
  -d DEVICE_TYPE, --device-type DEVICE_TYPE
                        Netmiko device driver i.e 'cisco_ios'.
  -c COMMAND, --command COMMAND
                        Command to run.
  -u, --use-textfsm     Use textFSM to transform command output.
  -p, --pprint          Use pretty print to display command output.
  -j, --json            Display as json.

Json output option should be used together with -u option structured output.

Imagine that you need structured command output to prepare mock files.

$ ./cli.py -d cisco_ios -c "show ip int br" -u -j
[
    {
        "intf": "Ethernet0/0",
        "ipaddr": "unassigned",
        "proto": "up",
        "status": "up"
    },
    {
        "intf": "Ethernet0/0.11",
        "ipaddr": "10.0.1.38",
        "proto": "up",
        "status": "up"
    },
    {
        "intf": "Ethernet0/1",
        "ipaddr": "1.1.1.1",
        "proto": "up",
        "status": "up"
    },
    {
        "intf": "Ethernet0/2",
        "ipaddr": "unassigned",
        "proto": "down",
        "status": "administratively down"
    },
    {
        "intf": "Ethernet0/3",
        "ipaddr": "unassigned",
        "proto": "down",
        "status": "administratively down"
    },
    {
        "intf": "Loopback0",
        "ipaddr": "10.0.1.2",
        "proto": "up",
        "status": "up"
    }
]

You can save this output as show_ip_interface_brief.json and use it to mock up netmiko output in your tests.