Templating/automating configuration

tim at pelican.org tim at pelican.org
Wed Jun 7 09:23:33 CST 2017


Hi Brian,

On Tuesday, 6 June, 2017 21:48, "Brian Knight" <ml at knight-networks.com> said:

> Because we had different sources of truth which were written in-house, we wound up
> rolling our own template engine in Python. It took about 3 weeks to write the
> engine and adapt existing templates.  Given a circuit ID, it generates the full
> config for copy and paste into a terminal session.  It also hooks into a
> configuration parser tool, written in-house, that tracks configured interfaces, so
> it is easy to see whether the template would overwrite an existing interface.

Interesting.  I'm going through much the same process at the moment, due to similar requirements - multiple sources of truth, validation that there's no clash with existing configs, but also with a requirement for network-wide atomic operations.  The latter has been a strong driver for a custom tool - it's now grabbing an exclusive lock on all the devices, making all the checks, pushing all the config, commit check everywhere, commit everywhere, and only once all the commits succeed, release the locks.  If any of those steps fail anywhere, we get to roll back everywhere.  (Obviously with appropriate timeouts / back-offs / deadlock prevention, and specific to platforms with sane config management - no vanilla IOS).

Did you find anything to give you a leg-up on config parsing, or did you have to do that completely from scratch?  At the moment, I'm working with PyEZ (I know, vendor lock-in, but we're firmly a Juniper shop, and going in eyes-open to the lock-in) to build a limited model of just the parts of the config I'm interested in validating, and it seems to be working.

> If I had a free hand and unlimited budget, I would find a single app that
> functions as a source of truth for all circuits and products, which includes a
> templating engine that hooks in easily.

Plus the business buy-in and the resource to go back and standardise all the existing configs, so the application can fully parse and understand the network before it starts.  That, and a pony :)

Regards,
Tim.




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