The designers of Cumulus Linux CLI were always focused on simplifying network device configurations. One of the first features along these lines was BGP across unnumbered interfaces, then they introduced simplified EVPN configurations, and recently auto-MLAG and auto-BGP.

You can watch a short description of these features by Dinesh Dutt and Pete Lumbis in Simplify Network Configuration with Cumulus Linux and Smart Datacenter Defaults videos (part of Cumulus Linux section of Data Center Fabrics webinar).

This blog post was initially sent to the subscribers of our SDN and Network Automation mailing list. Subscribe here.

Most automation projects are gradual improvements of existing manual processes, but every now and then the stars align and you get a perfect storm, like what Adrian Giacommetti encountered during one of his automation projects.

The customer had well-defined security policies implemented in Cisco ACI environment with tenants, endpoint groups, and contracts. They wanted to recreate those tenants in a public cloud, but it took way too long as the only migration tool they had was an engineer chasing GUI screens on both platforms.

The idea of redistributing the full Internet routing table (840.000 routes at this moment) into OSPF sounds as ridiculous as it is, but when fat fingers strike, it should be relatively easy to recover, right? Just turn off redistribution (assuming you can still log into the offending device) and move on.

Wrong. As Dmytro Shypovalov explained in an extensive blog post, you might have to restart all routers in your OSPF domain to recover.

And that, my friends, is why OSPF is a single failure domain, and why you should never run OSPF between your data center fabric and servers or VM appliances.

Anyone using text files as a poor man’s database eventually stumbles upon the challenge left as a comment in Automating Cisco ACI Environments blog post:

The biggest challenge we face is variable preparation and peer review process before committing variables to Git. I’d be particularly interested on how you overcome this challenge?

We spent hours describing potential solutions in Validation, Error Handling and Unit Tests part of Building Network Automation Solutions online course, but if you never built a network automation solution using Ansible YAML files as source-of-truth the above sentence might sound a lot like Latin, so let’s make it today’s task to define the problem.

In last week’s update session we covered the new features AWS introduced since the creation of AWS Networking webinar in 2019:

• AWS Local Zones, Wavelengths, and Outposts
• VPC Sharing
• Bring Your Own Addresses
• IP Multicast support
• Managed Prefix Lists in security groups and route tables
• VPC Traffic Mirroring
• Web Application Firewall
• AWS Shield
• VPC Ingress Routing
• Inter-region VPC peering with Transit Gateways

The videos are already online; you need Standard or Expert ipSpace.net subscription to watch them.

I was telling you there’s no need to become a programmer over six years ago, but of course nobody ever listens to grumpy old engineers… which didn’t stop Ethan Banks from writing another excellent advice on the same theme: Don’t Become A Developer, But Use Their Tools.

We all knew it for a long time, now it’s finally official: IP fragmentation is broken, or as the ever-so-diplomatic IETF likes to call it, IP Fragmentation is Considered Fragile.

This podcast introduction was written by Nick Buraglio, the host of today’s podcast.

In the original days of this podcast, there were heavy, deep discussions about this new protocol called “OpenFlow”. Like many of our most creative innovations in the IT field, OpenFlow came from an academic research project that aimed to change the way that we as operators managed, configured, and even thought about networking fundamentals.

For the most part, this project did what it intended, but once the marketing machine realized the flexibility of the technology and its potential to completely change the way we think about vendors, networks, provisioning, and management of networking, they were off to the races.

We all know what happened next.

Got this question from one of my long-time readers:

I am looking for commercial SDN solutions that can be deployed on top of brownfield networks built with traditional technologies (VPC/MLAG, STP, HSRP) on lower-cost networking gear, where a single API call could create a network-wide VLAN, or apply that VLAN to a set of ports. Gluware is one product aimed at this market. Are there others?

The two other solutions that come to mind are Apstra AOS and Cisco NSO. However, you probably won’t find a simple solution that would do what you want to do without heavy customization as every network tends to be a unique snowflake. 

Before we start: if you’re new to my blog (or stumbled upon this blog post by incident) you might want to read the Considerations for Host-Based Firewalls for a brief overview of the challenge, and my explanation why flow-tracking tools cannot be used to auto-generate firewall policies.

As expected, the “you cannot do it” post on LinkedIn generated numerous comments, ranging from good ideas to borderline ridiculous attempts to fix a problem that has been proven to be unfixable (see also: perpetual motion).

One of my readers sent me this question (probably after stumbling upon a remark I made in the AWS Networking webinar):

You had mentioned that AWS is probably not using EVPN for their overlay control-plane because it doesn’t work for their scale. Can you elaborate please? I’m going through an EVPN PoC and curious to learn more.

It’s safe to assume AWS uses some sort of overlay virtual networking (like every other sane large-scale cloud provider). We don’t know any details; AWS never felt the need to use conferences as recruitment drives, and what little they told us at re:Invent described the system mostly from the customer perspective.

In mid-September, Carl Buchmann, Fred Hsu, and Thomas Grimonet had an excellent presentation describing Arista’s Ansible roles and collections. They focused on two collections: CloudVision integration, and Arista Validated Designs. All the videos from that presentation are available with free ipSpace.net subscription.

Want to know even more about Ansible and network automation? Join our 2-day automation event featuring network automation experts from around the globe talking about their production-grade automation solutions or tools they created, and get immediate access to automation course materials and reviewed hands-on exercises.

While I keep telling you that Google-sized solutions aren’t necessarily the best fit for your environment, some of the hyperscaler presentations contain nuggets that apply to any environment no matter how small it is.

One of those must-watch presentations is Fault Tolerance through Optimal Workload Placement together with a wonderful TL&DR summary by the one-and-only Todd Hoff of the High Scalability fame.

Justin Pietsch is back with another must-read article, this time focused on high-speed Ethernet switching ASICs. I’ve rarely seen so many adjacent topics covered in a single easy-to-read article.

James Miles got tons of really interesting questions while watching the Network Operating System Models webinar by Dinesh Dutt, and the only reasonable thing to do when he sent them over was to schedule a Q&A session with Dinesh to discuss them.

We got together last week and planned to spend an hour or two discussing the questions, but (not exactly unexpectedly) we got only halfway through the list in the time we had, so we’re continuing next week.

This is how far we’ve got: