In the previous blog post in this series, we explored some of the reasons IP uses per-interface (and not per-node) IP addresses. That model worked well when routers had few interfaces and mostly routed between a few LAN segments (often large subnets of a Class A network assigned to an academic institution) and a few WAN uplinks. In those days, the WAN networks were frequently implemented with non-IP technologies like Frame Relay or ATM (with an occasional pinch of X.25).

The first sign of troubles in paradise probably occurred when someone wanted to use a dial-up modem to connect to a LAN segment. What subnet (and IP address) do you assign to the dial-up connection, and how do you tell the other end what to use? Also, what do you do when you want to have a bank of modems and dozens of people dialing in?

When I wrote about the (non)impact of switching latency, I was (also) thinking about packet bursts jamming core data center fabric links when I mentioned the elephants in the room… but when I started writing about them, I realized they might be yet another red herring (together with the supposed need for large buffers in data center switches).

Here’s how it looks like from my ignorant perspective when considering a simple leaf-and-spine network like the one in the following diagram. Please feel free to set me straight, I honestly can’t figure out where I went astray.

Last week we pushed out netsim-tools release 0.6.2. It’s a maintenance release, so mostly full of bug fixes apart from awesome contributions by Leo Kirchner who

• Made vSRX 3.0 work on AMD CPU (warning: totally unsupported).
• Figured out how to use vagrant mutate to use virtualbox version of Cisco Nexus 9300v Vagrant box with libvirt

Other bug fixes include:

• Numerous fixes in Ansible installation playbook
• LLDP on all vSRX interfaces as part of initial configuration
• Changes in FRR configuration process to use bash or vtysh as needed
• connect.sh executing inline commands with docker exec

Johan Gustawsson wrote a lengthy blog post describing Telia’s approach to next-generation Internet backbone architecture… and it’s so refreshing seeing someone bringing to life what some of us have been preaching for ages:

• Simplify the network;
• Stop cramming ever-more-complex services into the network;
• Bloated major vendor NPUs implementing every magic ever envisioned are overpriced – platforms like Broadcom Jericho2 are good enough for most use cases.
• Return from large chassis-based stupidities to network-centric high availability.

I don’t know enough about optics to have an opinion on what they did there, but it looks as good as the routing part. It would be great to hear your opinion on the topic – write a comment.

In the Site Design part of Cisco SD-WAN webinar, David Penaloza described capabilities you can use when designing complex sites, like extending SD-WAN transport between SD-WAN edge nodes, or implementing high availability between them. He also explained how to track an Internet-facing interface and a service beyond its next hop.

TL&DR: No.

Here’s another never-ending vi-versus-emacs-type discussion: merchant silicon like Broadcom Trident cannot forward small (64-byte) packets at line rate. Does that matter, or is it yet another stimulating academic talking point and/or red herring used by vendor marketing teams to justify their high prices?

Here’s what I wrote about that topic a few weeks ago:

In the previous blog post in this series, we figured out that you might not need link-layer addresses on point-to-point links. We also started exploring whether you need network-layer addresses on individual interfaces but didn’t get very far. We’ll fix that today and discover the secrets behind IP address-per-interface design.

In the early days of computer networking, there were three common addressing paradigms:

After I created the Segment Routing lab to test the relationship between Node Segment ID (SID) and MPLS labels, I was just a minor step away from testing BGP-free core with SR-MPLS.

I added two nodes to my lab setup, this time using IOSv as those nodes need nothing more than EBGP support (and IOSv is tiny compared to IOS XE on CSR):

Minh Ha left a lengthy comment to my There’s No Recipe for Success blog post, adding an interesting perspective of someone who had to work really hard to overcome coming from a third-world country.

Ivan, I happened to read “Deep Work: Rules for Focused Success in a Distracted World” recently so I can attest that it does provide some valuable advices on how to do things well. Some of the overarching themes are stay focused and cut off unnecessary noise/drain the shallow. The author also suggests removing your social media account if you can’t see how it add values to your work/business, as social media can create attention disorder, seen in many young kids these days.

Ethan Banks wrote the best one-line description of the crazy stuff we have to deal with in his When Stretching Layer Two, Separate Your Fate blog post:

No application should be tightly coupled to an IP address. This common issue should really be solved by application architects rebuilding the app properly instead of continuing like it’s 1999 while screaming YOLO.

Not that his (or my) take on indisputable facts would change anything… At least we can still enjoy a good rant ;)