In the world of ubiquitous Ethernet and IP, it’s common to think that one needs addresses in packet headers in every layer of the protocol stack. We have MAC addresses, IP addresses, and TCP/UDP port numbers… and low-level addresses are assigned to individual interfaces, not nodes.

Turns out that’s just one option… and not exactly the best one in many scenarios. You could have interfaces with no addresses, and you could have addresses associated with nodes, not interfaces.

In one of my introductory Segment Routing videos, I made claims along the lines of “Segment Routing totally simplifies the MPLS control plane, replacing LDP and local labels allocated to various prefixes with globally managed labels advertised in IGP”

It took two years for someone to realize the stupidity over-simplification of what I described. Matjaž Strauss sent me this kind summary of my errors:

You’re effectively claiming that SRGB has to be the same across all devices in the network. That’s not true; routers advertise SIDs and must configure label swap operations in case SRGBs don’t match.

Wait, what? What is SRGB and why could it be different across devices in the same network? Also, trust IETF to take a simple idea and complicate it to support vendor whims.

Azure and AWS have decent documentation (I always found it relatively easy to figure out what they’re doing), but what they implemented is sometimes so far away from what we’re used to that it’s hard to bridge the gap. Here’s how Olle Wilhelmsson solved that challenge:

Seventeen years after I started working on my EIGRP book, the reverse engineering days were over: RFC 7868 is the definitive guide to modern EIGRP (I’m not familiar with at least half of the concepts mentioned in it).

Just in case you’re interested in a bit of historical trivia:

• My EIGRP deciphering history started a few years before the book was published. In mid-1990s I was asked (as an external trainer) to create an EIGRP course for Cisco EMEA Training.
• I’ve never seen any internal EIGRP documentation or code – everything I knew about EIGRP I’ve learned from trying out crazy stuff and deciphering debugging messages.
• Two of the RFC authors (Russ White and Don Slice) were the technical reviewers for my EIGRP book. Russ copiously rewrote my pidgin English into something understandable – if you like reading my blog posts today, you should (also) thank Russ.

During my interview with David Bombal I made a recommendation I find crucial for anyone serious about blogging:

Make sure you own your content.

There’s a simple reason for that rule: if you want to write quality content, you’ll have to invest a lot of time into it.

TL&DR: If you want to test BGP, OSPF, IS-IS, or SR-MPLS in a virtual lab, you might build the lab faster with netsim-tools release 0.6.

In the netsim-tools release 0.6 I focused on adding routing protocol functionality:

• IS-IS on Cisco IOS/IOS XE, Cisco NX-OS, Arista EOS, FRR, and Junos.
• BGP on the same set of platforms, including support for multiple autonomous systems, EBGP, IBGP full mesh, IBGP with route reflectors, next-hop-self control, and BGP/IGP interaction.
• Segment Routing with MPLS on Cisco IOS XE and Arista EOS.

You’ll also get:

I know the title sounds like a buzzword-bingo-winning clickbait, but it’s true. Adrian Giacometti decided to merge the topics of two ipSpace.net online courses and automated deployment of AWS security rules using Terraform within GitLab CI pipeline, with Slack messages serving as manual checks and approvals.

Not only did he do a great job mastering- and gluing together so many diverse bits and pieces, he also documented the solution and published the source code:

• Part 1: Cloud & Network automation challenge: Deploy Security Rules in a DevOps/GitOps world with AWS, Terraform, GitLab CI, Slack, and Python (special guest FastAPI)
• Part 2: AWS, Terraform and FastAPI
• Part 3: GitLab CI, Slack, and Python
• Source code: aegiacometti/devops_cloud_challenge · GitLab

Want to build something similar? Join our Network Automation and/or Public Cloud course and get started. Need something similar in your environment? Adrian is an independent consultant and ready to work on your projects.

One of the viewers of Rachel Traylor’s excellent ‌Graph Algorithms in Networks webinar sent me this feedback:

I think it is too advanced for my needs. Interesting but difficult to apply. I love math and I find it interesting maybe for bigger companies, but for a small company it is not possible to apply it.

While a small company’s network might not warrant a graph-focused approach (I might disagree, but let’s not go there), keep in mind that almost everything we do in IT rides on top of some sort of graph:

I’ve been saying the same thing for years, but never as succinctly as Alastair Cooke did in his Understand Your Single Points of Failure (SPOF) blog post:

The problem is that each time we eliminated a SPOF, we at least doubled our cost and complexity. The additional cost and complexity are precisely why we may choose to leave a SPOF; eliminating the SPOF may be more expensive than an outage cost due to the SPOF.

Obviously that assumes that you’re able to follow business objectives and not some artificial measure like uptime. Speaking of artificial measures, you might like the discussion about taxonomy of indecision.

Scott Berkun wrote another great article that’s equally applicable to the traditional notion of design (his specialty) and the network design. Read it, replace design with network design, and use its lessons. Here’s just a sample:

• Convincing people is a social process
• Aim for small wins, not conversions of belief systems
• Allies matter more than ideas
• Design maturity grows one step at a time.

In the last part of my chat with David Bombal we discussed interesting technologies networking engineers could focus on if they want to grow beyond pure packet switching (and voice calls, if you happen to believe VoIP is not just an application). We mentioned public clouds, automation, Linux networking, tools like Git, and for whatever reason concluded with some of my biggest blunders.

Recently I joked there’s significant difference between AWS and Azure launching features:

• AWS launches a production-ready feature that you can consume the next day.
• Azure launches a preview that might work in 6 months.

Those with long enough memories shouldn’t be surprised. It’s not the first time Microsoft is using the same tactics.

Minh Ha left another extensive comment on my Is Switching Latency Relevant blog post. As is usual the case, it’s well worth reading, so I’m making sure it doesn’t stay in the small print (this time interspersed with a few comments of mine in gray boxes)

I found Cisco apparently manages to scale port-to-port latency down to 250ns for L3 switching, which is astonishing, and way less (sub 100ns) for L1 and L2.

I don’t know where FPGA fits into this ultra low-latency picture, because FPGA, compared to ASIC, is bigger, and a few times slower, due to the use of Lookup Table in place of gate arrays, and programmable interconnects.

Scott submitted an interesting the comment to my Does Unequal-Cost Multipath (UCMP) Make Sense blog post:

How about even Large CLOS networks with the same interface capacity, but accounting for things to fail; fabric cards, links or nodes in disaggregated units. You can either UCMP or drain large parts of your network to get the most out of ECMP.

Before I managed to write a reply (sometimes it takes months while an idea is simmering somewhere in my subconscious) Jeff Tantsura pointed me to an excellent article by Erico Vanini that describes the types of asymmetries you might encounter in a leaf-and-spine fabric: an ideal starting point for this discussion.

The reader asking about infrastructure-as-code in public cloud deployments also wondered whether he has any chance at mastering on-premises network automation due to lack of programming skills.

I am starting to get concerned about not knowing automation, IaC, or any programming language. I didn’t go to college, like a lot of my peers did, and they have some background in programming.

First of all, thanks a million to everyone needs to become a programmer hipsters for thoroughly confusing people. Now for a tiny bit of reality.