Antonio Boj sent me this interesting challenge:

Is there any way to avoid, prevent or at least mitigate bridging loops when using VXLAN with EVPN? Spanning-tree is not supported when using VXLAN encapsulation so I was hoping to use EVPN duplicate MAC detection.

MAC move dampening (or anything similar) doesn’t help if you have a forwarding loop. You might be able to use it to identify there’s a loop, but that’s it… and while you’re doing that your network is melting down.

Network automation is scary when you start using it in a brownfield environment. After all, it’s pretty easy to propagate an error to all devices in your network. However, there’s one thing you can do that’s usually pretty harmless: collect data from network devices and create summary reports or graphs.

I collected several interesting solutions created by attendees of our Building Network Automation Solutions online course and described them in a short video.

Want to create something similar? No time to procrastinate – the registration for the Spring 2019 course ends tomorrow.

This is a guest blog post by Andrea Dainese, senior network and security architect, and author of UNetLab (now EVE-NG) and  Route Reflector Labs. These days you’ll find him busy automating Cisco ACI deployments.

In this post we’ll focus on a simple question that arises in numerous chats I have with colleagues and customers: how should a network engineer operate Cisco ACI? A lot of them don’t use any sort of network automation and manage their Cisco ACI deployments using the Web Interface. Is that good or evil? As you’ll see we have a definite answer and it’s not “it depends”.

A while ago we published a guest blog post by Christoph Jaggi explaining the high-level security challenges of most SD-WAN solutions… but what about the low-level details?

Sergey Gordeychik dived deep into implementation details of SD-WAN security in his 35C3 talk (slides, video).

TL&DW: some of the SD-WAN boxes are as secure as $19.99 Chinese webcam you bought on eBay.

Numerous network automation deployments happen in brownfield installations: you’re trying to automate parts of existing network deployment and operations processes. If you’re lucky you start automating deployment of new devices… but what if you have to automate parts of existing device configurations?

I spent most of last week with a great team of fellow networking and security engineers in a windowless room listening to good, bad and plain boring presentations from (mostly) Cisco presenters describing new technologies and solutions – the yearly Tech Field Day Extra @ Cisco Live Europe event.

This year’s hit rate (the percentage of good presentations) was about 50% and these are the ones I found worth watching (in chronological order):

Not that it helps that much but keep in mind: you're not the only one. Here's a wonderful blog post by Al Rasheed.

Oh, and if you still feel like a fraud after being in the industry for years (check out the Impostor Syndrome), you're not alone either.

Erik Dietrich (of the Expert Beginner fame) published another great blog post explaining when and why you should write a book. For the attention-challenged here’s my CliffNotes version:

• Realize you have no idea what you’re doing (see also: Dunning-Kruger effect)
• Figure out why you’d want to spend a significant amount of your time on a major project like book writing;
• It will take longer (and will be more expensive) than you expect even when considering Hofstadter’s law.

I got some interesting feedback from one of my readers on Segment Routing with IPv6 extension headers:

Some people position SRv6 as the universal underlay and overlay due to its capabilities for network programming by means of feature+locator SRH separation.

Stupid me replied “SRv6 is NOT an overlay solution but a source routing solution.”

Remember how earlier releases of Nexus-OS started dropping configuration commands if you were typing them too quickly (and how it was declared a feature ;)?

Mark Fergusson had a similar experience on Cisco IOS. All he wanted to do was to use Ansible to configure a VRF, an interface in the VRF, and OSPF routing process on Cisco CSR 1000v running software release 15.5(3).

Here’s what he was trying to deploy. Looks like a configuration straight out of an MPLS book, right?