After finishing the network automation part of a recent SDN workshop I told the attendees “Vote with your wallet. If your current vendor doesn’t support the network automation functionality you need, move on.”

Not surprisingly, the next question was “And what shall we ask for?” Here’s a short list of ideas, please add yours in comments.

One of my readers sent me this question:

I often see designs involving several more than 2 DCs spread over different locations. I was actually wondering if that makes sense to bring high availability inside the DC while there's redundancy in place between the DCs. For example, is there a good reason to put a cluster of firewalls in a DC, when it is possible to quickly fail over to another available DC, as a redundant cluster increases costs, licenses and complexity.

Rule#1 of good engineering: Know Your Problem ;) In this particular case:

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One of my readers sent me an interesting question after reading my ICMP Redirects blog post:

In Cisco IOS, when a packet is marked by IOS for ICMP redirect to a better gateway, that packet is being punted to the CPU, right?

It depends on the platform, but it’s going to hurt no matter what.

We got pretty far in our Data Center optimization journey. We virtualized the workload, got rid of legacy technologies, and reduced the number of server uplinks and replaced storage arrays with distributed file system.

Final step on the journey: replace physical firewalls and load balancers with virtual appliances.

My friend Matthias Luft sent me an interesting tweet a while ago:

@ioshints What’s your take on firewall rule sets & IP addresses vs. hostnames?

— Matthias Luft (@uchi_mata) August 16, 2016

All I could say in 160 characters was “it depends”. Here’s a longer answer.

Just wanted to point you to two excellent blog posts recently published by Russ White.

Reaction: DevOps and Dumpster Fires

If teaching coders isn’t going to solve the problem, then what do we do? We need to go to where the money is. Applications aren’t bought by coders, just like networks aren’t.

One of the attendees of my Building Next-Generation Data Center course asked this interesting question after listening to my description of differences between Chet/Puppet and Ansible:

For Zero-Touch Provisioning to work, an agent gets installed on the box as a boot up process that would contact the master indicating the box is up and install necessary configuration. How does this work with agent-less approach such as Ansible?

Here’s the first glitch: many network devices don’t ship with Puppet or Chef agent; you have to install it during the provisioning process.

One of my readers sent me interesting feedback after reading my explanation of why I’d try not to use OSPF as a routing protocol between hosts and ToR switches. He said:

Unfortunately we can’t use BGP because IBM mainframes support only OSPF or RIP, so we decided to use VRFs instead.

Here’s what they did:

Marco Canini from UC Louvain is working on an IXP research project focused on bringing privacy guarantees into Internet routing context. They’re trying to understand the privacy considerations of network operators and have created a short survey to gather the initial data.

Researchers from UC Louvain have been involved in tons of really useful projects including BGP PIC, LFA, MP-TCP, Fibbing, Software-defined IXP and flow-based load balancing, so if you’re connected to an IXP, please take your time and fill in the survey.

In March 2016 my friend Matt Oswalt announced a distributed network testing framework that he used for validation in his network automation / continuous integration projects. Initial tests included ping and DNS probes, and he added HTTP testing in May 2016.

The project continues to grow (and already got its own Github and documentation page) and Matt was kind enough to share the news and future plans in Episode 63 of Software Gone Wild.

To ask questions about the project, join the Todd channel on networktocode Slack team (self-registration at slack.networktocode.com)

One of my friends plans to replace existing FabricPath data center infrastructure, and asked whether it would make sense to stay with FabricPath (using the new Nexus 5600 switches) or migrate to ACI.

I proposed a third option: go with simple VXLAN encapsulation on Nexus 9000 switches. Here’s why:

One of my readers watched my TCP, HTTP and SPDY webinar and disagreed with my assertion that shaping sometimes works better than policing.

TL&DR summary: policing = dropping excess packets, shaping = delaying excess packets.

Here’s the picture he sent me (watch the video to get the context and read this article to get the background details):

One of my readers had problems getting the NFV big picture (and how it relates to SDN):

I find the topic area of SDN and NFV a bit overwhelming in terms of information, particularly the NFV bit.

NFV is a really simple concept (network services packaged in VM format), what makes it complex is all the infrastructure you need around it.

One of my friends sent me this question:

How many VM moves do you see in a medium and how many in a large data center environment per second and per minute? What would be a reasonable maximum?

Obviously the answer to the first part is it depends (please share your experience in the comments), so we’ll focus on the second one. It’s time for another Fermi estimate.