Data Center BGP: Autonomous Systems and AS Numbers

Two weeks ago we discussed whether it makes sense to use BGP as the routing protocol in a data center fabric. Today we’ll tackle three additional design challenges:

• Should you use IBGP or EBGP?
• When should you run BGP on the spine switches?
• Should every leaf switch have a different AS number or should they share the same AS number?

Create IP Multicast Tree Graphs from Operational Data

A while ago I created an Ansible playbook that creates network diagrams from LLDP information. Ben Roberts, a student in my Building Network Automation Solutions online course used those ideas to create an awesome solution: he’s graphing multicast trees.

Here’s how he described his solution:

Moving Complexity to Application Layer?

One of my readers sent me this question:

One thing that I notice is you mentioned moving the complexity to the upper layer. I was wondering why browsers don't support multiple IP addresses for a single site – when a browser receives more than one IP address in a DNS response, it could try to perform TCP SYN to the first address, and if it fails it will move to the other address. This way we don't need an anycast solution for DR site.

Of course I pointed out an old blog post ;), and we all know that Happy Eyeballs work this way.

First Speakers in the Spring 2018 Automation Online Course

For the first two sessions of the Building Network Automation Solutions online course I got awesome guest speakers, and it seems we’ll have another fantastic lineup in the Spring 2018 course:

Most network automation solutions focus on device configuration based on user request – service creation or change of data model describing the network. Another very important but often ignored aspect is automatic response to external events, and that’s what David Gee will describe in his presentation.

New Content: Debugging Ansible Playbooks and Jinja2 Templates

Here’s a quote from one of my friends who spent years working with Ansible playbooks:

Debugging Ansible is one of the most terrible experiences one can endure…

It’s not THAT bad, particularly if you have a good debugging toolbox. I described mine in the Debugging Ansible Playbooks part of the Ansible for Networking Engineers online course.

Please note that the Building Network Automation Solutions online course includes all material from the Ansible online course.

Worth Reading: Postpone Inbox Procrastination

This blog post by Ethan Bank totally describes my (bad) Inbox habits. If you're anything like me, you might find Ethan's ideas useful (I do... following them is a different story though).

Video: Switch Buffer Architectures

A while ago (in the time of big-versus-small buffers brouhaha) I asked JR Rivers to do a short presentation focusing on buffering requirements of data center switches. He started by describing typical buffer architectures you might find in data center switches.

Response: Upgrading Network Device Software

I got numerous responses to the “Why Does It Take So Long to Upgrade Network Devices,” the best ones coming from Béla Várkonyi and Frederic Cuiller.

Béla is sick-and-tired of the stuff vendors are shipping:

Automate Remote Site Hardware Refresh Process

Every time we finish the Building Network Automation Solutions online course I ask the attendees to share their success stories with me. Stan Strijakov was quick to reply:

I have yet to complete the rest of the course and assignments, but the whole package was a tremendous help for me to get our Ansible running. We now deploy whole WAN sites within an hour.

Of course I wanted to know more and he sent me a detailed description of what they’re doing:

Stop Googling and Start Testing

Here’s a question I got on one of my ancient blog posts:

How many OSPF process ID can be used in a single VRF instance?

Seriously? You have to ask that? OK, maybe the question isn’t as simple as it looks. It could be understood as:

Simplifying ipSpace.net Products

When I started my ipSpace.net project life was simple: I had a few webinars, and you could register for the live sessions. After a while I started adding recordings, subscriptions, bundles, roadmaps (and tracks), books… and a few years later workshops and online courses.

As you can imagine, the whole thing became a hard-to-navigate mess. Right now you can buy almost 70 different products on ipSpace.net. Time for a cleanup.

Worth Reading: The Basic Math behind Reliability

Diptanshu Singh wrote a nice explanation of the math behind reliability calculations. Definitely worth reading even if you hated statistics.

Tool-of-the-day: Isochronous Round-Trip-Tester

Dave Taht sent me a link to IRTT after I published a blog post on measuring end-to-end latency with an Ansible playbook. Definitely looks like a tool worth having in your toolbox.

How Did NETCONF Start on Software Gone Wild

A long while ago Marcel Wiget sent me an interesting email along the lines “I think you should do a Software Gone Wild podcast with Phil Shafer, the granddaddy of NETCONF”

Not surprisingly, as we started discovering the history behind NETCONF we quickly figured out that all the API and automation hype being touted these days is nothing new – some engineers have been doing that stuff for almost 20 years.

Automate End-to-End Latency Measurements

Here’s another idea from the Building Network Automation Solutions online course: Ruben Tripiana decided to implement a latency measurement tool. His playbook takes a list of managed devices from Ansible inventory, generates a set of unique device pairs, measures latency between them, and produces a summary report (see also his description of the project).

BGP as a Better IGP? When and Where?

A while ago I helped a large enterprise redesign their data center fabric. They did a wonderful job optimizing their infrastructure, so all they really needed were two switches in each location.

Some vendors couldn’t fathom that. One of them proposed to build a “future-proof” (and twice as expensive) leaf-and-spine fabric with two leaves and two spines. On top of that they proposed to use EBGP as the only routing protocol because draft-lapukhov-bgp-routing-large-dc – a clear case of missing the customer needs.

Security or Convenience, That’s the Question

One of my readers was so delighted that something finally happened after I wrote about a NX-OS bug that he sent me a pointer to another one that has been pending for a long while, and is now officially terminated as FAD (Functions-as-Designed… even documented in the Further Problem Description).

Here’s what he wrote (slightly reworded)…

It’s Bash Scripts All the Way Down (more on CLI versus API)

Netfortius made an interesting comment to my Ansible playbook as a bash script blog post:

Ivan - aren't we now moving the "CLI"[-like] approach, upstream (the one we are just trying to depart, via the more structured and robust approach of RESTAPI).

As I explained several times, I don’t know where the we must get rid of CLI ideas are coming from; the CLI is root of all evil mantra is just hype generated by startups selling alternative approaches (the best part: one of them was actually demonstrating their product using CLI).

New Video: Whitespace Handling in Jinja2

Whitespace handling is one of the most confusing aspects of Jinja2, thoroughly frustrating many attendees of my Ansible and Network Automation online courses.

I decided to fix that, ran a few well-controlled experiments, and documented the findings and common caveats in Whitespace Handling in Jinja2 video.

Video: Using Simple PowerShell Scripts

After explaining the basics of PowerShell, Mitja Robas described how to do implement the “Hello, World!” of network automation (collecting printouts from network devices) in PowerShell.

To watch all videos from this free webinar, register here.