This is a common objection I get when trying to persuade network architects they don’t need stretched VLANs (and IP subnets) to implement data center disaster recovery:
Changing IP addresses when activating DR is hard. You’d have to weigh the manageability of stretching L2 and protecting it, with the added complexity of breaking the two sites into separate domains [and subnets]. We all have apps with hardcoded IP’s, outdated IPAM’s, Firewall rules that need updating, etc.
Let’s get one thing straight: when you’re doing disaster recovery there are no live subnets, IP addresses or anything else along those lines. The disaster has struck, and your data center infrastructure is gone.Read more ...
Design assignments and hands-on exercises were always a big part of ipSpace.net online courses, and our new Networking in Public Cloud Deployments course is no different.
You’ll start with a simple scenario: deploy a virtual machine running a web server. Don’t worry about your Linux skills, you’ll get the necessary (CCIE-level) instructions and the source code for the web server. Building on that, you’ll create another subnet and deploy another virtual machine acting as a back-end application server.
And then we’ll get to the fun part:Read more ...
Got this interesting question from one of my readers:
BGP EVPN message carries both VNI and RT. In importing the route, is it enough either to have VNI ID or RT to import to the respective VRF?. When importing routes in a VRF, which is considered first, RT or the VNI ID?
A bit of terminology first (which you’d be very familiar with if you ever had to study how MPLS/VPN works):Read more ...
Is your argument that the technology works as designed and any issues with it are a people problem?
A polite question like that deserves more than 280-character reply, but I tried to do my best:
BGP definitely works even better than designed. Is that good enough? Probably, and we could politely argue about that… but the root cause of most of the problems we see today (and people love to yammer about) is not the protocol or how it was designed but how sloppily it’s used.
Laura somewhat disagreed with my way of handling the issue:Read more ...
A month ago I described how Paddy Kelly used pyATS to get VRF data from a Cisco router to create per-VRF connectivity graphs.
Recently he also wrote a short article describing how to get started with pyATS and Ansible. Thank you, Paddy!
You need Free ipSpace.net Subscription to watch the video, and the Standard ipSpace.net Subscription to register for a deeper dive into cloud security with Matthias Luft (next live session on December 10th: Identity and Access Management).
One of the responses to my Disaster Recovery Faking blog post focused on failure domains:
What is the difference between supporting L2 stretched between two pods in your DC (which everyone does for seamless vMotion), and having a 30ms link between these two pods because they happen to be in different buildings?
I hope you agree that a single broadcast domain is a single failure domain. If not, let agree to disagree and move on - my life is too short to argue about obvious stuff.Read more ...
Two weeks ago Nicola Modena explained how to design BGP routing to implement resilient high-availability network services architecture. The next step to tackle was obvious: how do you fine-tune convergence times, and how does BGP convergence compare to the more traditional FHRP-based design.
You’ve probably heard cloudy evangelists telling CIOs how they won’t need the infrastructure engineers once they move their workloads into a public cloud. As always, whatever sounds too good to be true usually is. Compute resources in public clouds still need to be managed, someone still needs to measure application performance, and backups won’t happen by themselves.
Even more important (for networking engineers), network requirements don’t change just because you decided to use someone else’s computers:Read more ...
I stumbled upon a great MIT Technology Review article (warning: regwall ahead) with a checklist you SHOULD use whenever considering a machine-learning-based product.
While the article focuses on machine learning at least some of the steps in that list apply to any new product that claims to use a brand new technology in a particular problem domain like overlay virtual networking with blockchain:Read more ...
No, we were not talking about IP fabrics in general - IP Fabric is a network management software (oops, network assurance platform) Gian Paolo discovered a while ago and thoroughly tested in the meantime.
He was kind enough to share what he found in Episode 107 of Software Gone Wild, and as Chris Young succinctly summarized: “it’s really sad what we still get excited about something 30 years after it was first promised”… but maybe this time it really works ;)
The registration is still open for the Using VXLAN to Build Active-Active Data Centers workshop on December 3rd, but if you can’t make it to Zurich you might enjoy these live sessions we’ll run in December 2019:
Someone sent me this observation after reading my You Cannot Have Public Cloud without Networking blog post:
As much as I sympathize with your view, scales matter. And if you make ATMs that deal with all the massive client population, the number of bank tellers needed will go down. A lot.
Based on what I read a while ago a really interesting thing happened in financial industry: while the number of tellers went down, number of front-end bank employees did not go down nearly as dramatically, they just turned into “consultants”.Read more ...
Got an interesting set of questions from a networking engineer who got stuck with the infamous “let’s push the **** down the stack” challenge:
So I am a rather green network engineer trying to solve the typical layer two stretch problem.
I could start the usual “friends don’t let friends stretch layer-2” or “your business doesn’t really need that” windmill fight, but let’s focus on how the vendors are trying to sell him the “perfect” solution:Read more ...
I’m running two workshops in Zurich in the next 10 days:
I published the slide deck for the NSX versus ACI workshop a few days ago (and you can already download it if you have a paid ipSpace.net subscription) and it’s full of new goodness like ACI vPod, multi-pod ACI, multi-site ACI, ACI-on-AWS, and multi-site NSX-V and NSX-T.
Steve Bellovin wrote a great series of articles describing the early history of Usenet. The most interesting part in the “security and authentication” part was probably this gem:
That left us with no good choices. The infrastructure for a cryptographic solution was lacking. The uux command rendered illusory any attempts at security via the Usenet programs themselves. We chose to do nothing. That is, we did not implement fake security that would give people the illusion of protection but not the reality.
A lot of other early implementers chose the same route, resulting in SMTP, BGP… which wouldn’t be a problem if someone kept track of that and implemented security a few years later. Unfortunately we considered those problems solved and moved on to chase other squirrels. We’re still paying the interest on that technical debt.
Another great advice from Charity Majors: does it make sense to go back to being an engineer after being a manager for a few years?
Personal note: finding a great replacement for my CTO role was probably the best professional decision I ever made ;)
As always, no good deed goes unpunished - “creative” individuals trying to force-fit their mis-designed star-shaped pegs into round holes, and networking vendors looking for competitive advantage quickly destroyed the idea with tons of middlebox devices, ranging from firewalls and load balancers to NAT, WAN optimization, and DPI monstrosities.