Jsicuran left this comment on my You Must Understand the Fundamentals to Be Successful blog post:

I just went through some Cisco webinar where they were showcasing the use of NX-OS API and Python to add a VLAN. I do some Python myself and have used that API for some simple DevOps-like uses, but for the most part if you are an enterprise and use Prime DCIM to add VLANs, why should you go through the coding process?

It obviously depends on where you are in your IT automation journey.

Great news for everyone trying to deploy IPv6 in OpenStack: the Kilo release has full support for IPv6 in the tenant networks, including SLAAC, stateless and stateful DHCPv6. For more details, read an extensive blog post by Shannon McFarland.

When I finished my SDN workshop @ Interop Las Vegas (including a chapter on OpenFlow limitations), some attendees started wondering whether they should even consider OpenFlow in their SDN deployments. My answer: don’t blame the tool if people use it incorrectly.

Two days later, I discovered HP is one of those companies that knows how to use that tool.

John Jackson wrote an interesting comment on my Rearchitecting L3-Only Networks blog post:

What the host has configured for its default gateway doesn't really matter, correct? Because the default gateway in traditional L2 access networks really isn't about the gateway's IP address, but the gateway's MAC address. The destination IP address in the packet header is always the end destination IP address, never the default gateway.

He totally got the idea, however there are a few minor details to consider.

One of the topics I discussed in the IPv6 High Availability webinar is the problem of dual-stack deployments – what do you do when the end-to-end path for one of the protocol stacks breaks down. Happy eyeballs is one of the solutions, as is IPv6-only data center (Facebook is moving in that direction really fast). For more details, watch the short End-to-End High Availability in Dual Stack Networks video available with Free Subscription.

One of my readers sent me this question:

After reading this blog post and a lot of blog posts about zero trust mode versus security zones, what do you think about replacing L3 Data Center core switches by High Speed Next Generation Firewalls?

Long story short: just because someone writes about an idea doesn’t mean it makes sense. Some things are better left in PowerPoint.

I recently read a must-read blog post by Russ White in which he argued that you need to understand both theory and practice (see also Knowledge or Recipes and my other certification rants) and got a painful flashback of a discussion I had with a corner-cutting SE (fortunately he was an exception) almost two decades ago when I was teaching my Advanced OSPF course at Cisco.

I was talking about “application-layer gateways” on firewalls and NAT boxes with a fellow engineer, and we came to an interesting conclusion: in most cases they are not gateways; they don’t add any significant functionality apart for payload fixups for those broken applications that think carrying network endpoint information in application packets is a good idea (I’m looking at you, SIP and FTP). These things should thus be called Application Layer Fixups or ALFs ;)

Whenever software switching nerds get together and start discussing the challenges of high-speed x86-based switching, someone inevitably mentions PF_RING, an open-source library that gives you blazingly fast packet processing performance on a Linux server.

I started recording a podcast with Luca Deri, the author of PF_RING, but we diverted into discussing ntopng, Luca’s network monitoring software. We quickly fixed that and recorded another podcast – this time, it’s all about PF_RING, and we discussed these topics:

25 years ago when I started my networking career, mainframes were all the rage, and we were doing some crazy stuff with small distributed systems that quickly adapted to topology changes, and survived link, port, and node failures. We called them routers.

Yes, we were crazy and weird, but our stuff worked. We won and we built the Internet, proving that we can build networks bigger than any mainframe-based solution could ever hope to be.

One of my readers was reading the Preparing an IPv6 Addressing Plan document on RIPE web site, and found that the document proposes two approaches to IPv6 addressing: encode location in high-order bits and subnet type in low-order bits (the traditional approach) or encode subnet type in high-order bits and location in low-order bits (totally counter intuitive to most networking engineers). His obvious question was: “Is anyone using type-first addressing in production network?”

Terastream project seems to be using service-first format; if you’re doing something similar, please leave a comment!

A long long time ago Colin Dixon wrote the following tweet in response to my Controller Cluster Is a Single Failure Domain blog post:

He’s obviously right, but I wasn’t talking about interconnected domains, but failure domains (yeah, I know, you could argue they are the same, but do read on).

Every now and then someone actually looks at the VXLAN packet format and eventually figures out that VXLAN encapsulation doesn’t provide any intrinsic security.

TL&DR Summary: That’s old news, the sky is not falling, and deploying VXLAN won’t make your network less secure than traditional VLAN- or MPLS-based networks.

Whenever I’m running an SDDC workshop or doing on-site SDN/SDDC-related consulting, the question of hardware gateways between overlay virtual networks and physical world inevitably pops up.

My usual answer: You have to understand (A) what type of gateway you need, (B) what performance you need and (C) what form factor will give you that performance. For more details, watch the Hardware Gateways video from Scaling Overlay Virtual Networks webinar

One of the responses I got on my “What is Layer-2” post was

Ivan, are you saying to use L3 switches everywhere with /31 on the switch ports and the servers/workstation?

While that solution would work (and I know a few people who are using it with reasonable success), it’s nothing more than creative use of existing routing paradigms; we need something better.