Category: automation

It looks like JSON Schema is the new black. Last week I wrote about a new Ansible module using JSON Schema to validate data structures passed to it; a few weeks ago NetworkToCode released Schema Enforcer, a similar CLI tool (which means it’s easy to use it in any CI/CD pipeline).

Here are just a few things Schema Enforcer can do:

A few months ago I described how you could use JSON Schema to validate your automation data models, host/group variable files, or even Ansible inventory file.

I had to use a weird toolchain to get it done – either ansible-inventory to build a complete data model from various inventory sources, or yq to convert YAML to JSON… and just for the giggles jsonschema CLI command requires the JSON input to reside in a file, so you have to use a temporary file to get the job done.

In January, Jason Edelman kindly invited me for a chat about the state of (software defined) networking and network automation in particular. The recording was recently published on Network Collective.

Last year I wrote an article describing data model optimization going from a simple this is what we need to configure individual devices to a highly polished high-level network nodes and links model. Not surprisingly, as Jeremy Schulman was quick to point out, the latter one had Jinja2 templates you wouldn’t want to debug. Ever. You can’t run away from complexity… but you can manage it.

Many successful network automation solutions (example: Cisco NSO) solve the “we’d love to work with high-level data models but hate complex templates” challenge with data transformation: operators work with an abstracted data model describing services, nodes and links, and the device configuration templates use low-level data derived from the abstracted data models through a series of business logic rules or lookups (aka network design).

Long long time ago in a country far far away when traveling was still a thing I led an interesting data center fabric design workshop. We covered tons of interesting topics, including automating network services deployments (starting with VLAN self-service for server admins).

As was often the case in my workshops, we had representatives from multiple IT teams sitting in the room, and when I started explaining how I’d automate VLAN deployments, the server administrator participating in the workshop quickly chimed in: “that’s exactly how I implemented self-service for some of our customers, it makes perfect sense to use the same approach for server port and VLAN provisioning”, and everyone else in the room agreed… apart from the networking engineer, who used a counter-argument along the lines of “we only provision a new VLAN or server port every few days, we can do it by hand” and no amount of persuasion would move him.

In the last weeks I described the challenges you might face when converting XML documents that contain lists with a single element into JSON, be it on device (Nexus OS) or in an Ansible module. Now let’s see how we can fix that.

There’s one more thing I feel needs to be done before I go for that coffee break: a webinar focusing on network automation concepts (as opposed to replacing Excel with YAML and Ansible or Becoming a Python Coder). Here’s a rough list of concepts I think should be in there:

• Data models and data stores
• Data model transformations
• Single source of truth
• Abstraction layers
• Idempotency

Last week I wrote about the interesting challenges you might encounter when using data generated by a Junos device in an Ansible playbook. Unfortunately it’s not just Junos – every system built around XML-based data structures might experience the same issues, including Cisco Nexus OS.

When you want to transport a complex data structure between components of a distributed system you’re usually using a platform-independent data encoding format like XML, YAML, or JSON.

XML was the hip encoding format in days when Junos and Cisco Nexus OS was designed and lost most of its popularity in the meantime due to its complexity (attributes, namespaces…) that makes it hard to deal with XML documents in most programming languages.

JSON is the new cool kid on the block. It’s less complex than XML, maps better into data structures supported by modern programming languages, and has decently fast parser implementations.

Looks like some vendor marketers (you know, the same group of people who brought us the switching/routing/bridging stupidity) felt the need to go beyond the usual SDN and intent-based hype and started misusing the imperative versus declarative concepts. Unfortunately some networking engineers fell for the ploy; here’s a typical feedback along these lines I got from one of my readers:

I am frustrated by most people’s shallow understanding API’s, especially the differences between declarative (“what”) and imperative (“how”) API’s, and how that impacts one’s operations. Declarative APIs are the key pillar of what many vendors call “policy” or “intent-based” networking.

Let’s try to unravel that.

It’s amazing how quickly you can deploy new functionality once you have a solid foundation in place. In his latest blog post Adrian Giacometti described how he implemented a security solution that allows network operators to block source IP addresses (identified by security tools) across dozens of firewalls using a bot listening to a Slack channel.

Would you be surprised if I told you we covered similar topics in our automation course? 😇

Some networking engineers renew their ipSpace.net subscription every year, and when they drop off the radar, I try to get in touch with them to understand whether they moved out of networking or whether we did a bad job.

One of them replied that he retired after building a fully automated site deployment solution (first lesson learned: you’re never too old to start automating your network), and graciously shared numerous lessons learned while building that solution.

Recording the same content for the third time because software developers decided to write code before figuring out what needs to be done is disgusting… so it took me a long long while before I collected enough willpower to rewrite and retest all the examples and re-record the Getting Operational Data section of Ansible for Networking Engineers webinar.

The new videos explain how to consume data generated by show commands in JSON or XML format, and how to parse the traditional text-based show printouts. I dropped mentions of (semi)failed experiments like Ansible parse_cli and focused on things that work well: TextFSM, in particular with ntc-templates library, pyATS/Genie, and TTP. On the positive side, I liked the slick new cli_parse module… let’s hope it will stay that way for at least a few years.

On a totally unrelated topic, I realized (again) that fail fast, fail often sounds great in a VC pitch deck, and sucks when you have to deal with its results.

In the last part of his Cumulus Linux 4.0 Update Pete Lumbis talked about using NetQ to capture streaming telemetry and increase network observability, and the new model-driven configuration approach (including all the usual buzzwords like NETCONF, RPC, YAML, JSON, and OpenConfig) coming in 2020.

When restructuring our online courses we decided to make the video content that was previously part of Ansible online course available with Standard ipSpace.net Subscription.

If you haven’t enrolled into our automation online course (which always included the extra bits) you’ll find the following additional content in our Ansible for Networking Engineers webinar: