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In this article I expose my study notes on the VXLAN technology with the Nexus 9000 product family, in both NX-OS and ACI mode. What is the purpose of VXLAN? Any network engineer can tell that we have a limitation with VLANs: we can have a maximum of 4094 unique VLANs on a single layer 2 domain. And a VLAN stops at the layer 3 boundary, where routing devices take the role to transport packets from one location/datacenter to another. That means, whenever we want to apply Live Migration (or vMotion) to a workload on a datacenter X to swap it to datacenter Y will not possible. In this sense, VXLAN facilitates workload-anywhere strategy, which encompasses workload mobility and reachability. General definition of VXLAN A VXLAN is a layer 2 tunneling scheme (i.e group of virtual tunnels) formed over a layer 3 network that plays the role of (in our case) a transport network . The transport network is usually a regular IP network running static or dynamic routing protocols and is called the ...

I gather in this blog post different networking definitions a network engineer may encounter (or may not, what a shame, LOL) in his journey. It will be a short article but bare with me, there are tricky nuances! Administrative layer 2 domain the layer 2 domain – or part thereof – that a network engineer manages. Layer 2 domain the network formed by the sum total of switches, hubs and any layer 2 devices in a network. The layer 2 domain is delimited by the existence of a device performing a layer 3 (routing) function. Layer 2 segment a portion of the layer 2 domain. It is usually defined by either VLAN or VXLAN technology. VLAN segment the collection of network hosts and nodes that belong to the same VLAN ID. Hosts on one VLAN segment “A” can not communicate inherently with hosts on a VLAN segment “B” unless there is a routing component (a layer 3 gateway) that performs inter-VLAN routing. Multitenant datacenter a datacenter where multiple organisation...

Introduction An XML Sitemap is required to allow search engines to easily crawl and index your blog. As a full-time network engineer and hobby blogger, I had not much time to build my own sitemap. So, like all blog folks out there, I used plugins to generate it. This article shows you how a simple XML Sitemap error can hide more that you think. XML Sitemap error I got since more than 3 months a weird XML sitemap error message: XML declaration allowed only at the start of the document XML declaration allowed only at the start of the document I first thought it was due to the Yoast SEO plugin. Therefore I deactivated the Yoast-generated XML sitemap. deactivating yoast seo xml sitemap and installed another sitemap plugin which generated a correct (at least to my eyes) XML sitemap. However, Google search console still flags my blog as Soft 404. I spent whole weekends and vacation days trying to reverse engineer the reason behind this Google rejection. blog pages are excluded from google A...

Introduction Once I’ve finished college studies and entered the professional world, I had some regrets of not having continued my Master’s degree. At least 5 of my college classmates opted to continue studying to earn their Master’s degree. My excuse back then was “I do not want to study deeper Algebra and circuits. I’ve have enough of them. Besides, Master’s degree is for girls who want a stable job in academia.” I was spontaneous in my answer. But I was not completely wrong. Since I was graduating as Bachelor and having at the same time a CCNA certificate, I was confident in my ability to snatch a good job in network engineering. Back then in 2008, a CCNA was a pretty good value to hire. There are many types of college degrees. But if you are considering an Information Technology job, having a degree related to IT is helpful. This alone could save you a lot of time understanding the basics of computers. But if you don’t, it’s not t...

Using username "admin". Application Policy Infrastructure Controller admin@10.10.20.42's password: Last login: 2020-06-07T14:19:13.000+00:00 UTC apic1# After connecting to the CLI, press the tab key to list all possible commands: apic1# attach-ave configure export-config logit show attach-avs debug fabric passwd terminal bash end firmware reload trigger callhome eraseconfig import-config replace-controller where clear exit lastlogin apic1# apic1# show endpoints Legends: (P):Primary VLAN (S):Secondary VLAN Total Dynamic Endpoints: 0 Total Static Endpoints: 0 apic1# apic1# There is also the variation “show endpoint mac {MAC_ADDR}”. And the MAC address can be typed in one of the four possible formats: apic1# show endpoint mac ? E.E.E MAC address (Option 1) EE-EE-EE-EE-EE-EE MAC address (Option 2) EE:EE:EE:EE:EE:EE MAC address (Option 3) EEEE.EEEE.EEEE ...

Ever wondered about software-defined data centers? Well I guess you experimented a bit with VMware Workstation sometime in your networking journey. If not, then I hope you have heard of VMware vSphere, because in the following short article I expose my study notes on the topic. Terminology Having experimented with VMware Workstation in my college studies (to emulate Linux guest OSes such as Fedora, Suse and Red Hat), I worked later at a very high level with virtual servers that run on vSphere. A couple of examples of that would be Cisco VSOM and Cisco UCM 10.x heard that VMware vSphere is arguably the number 1 data center virtualization solution in the world. This suite does not run as a silo. It integrates with other VMware products. VMware offers the following vSphere editions: Standard Enterprise Enterprise Plus Operations Management with Enterprise Plus: this version has been discontinued because VMware wants to align its vSphere distributions to its standard release naming path. ...

In this article I expose my review of the Shift8 CDN solution, based on my own experience. What is Shift8? Shift8 is a provider of a free CDN solution that is compatible with WordPress. The company is based in Toronto. Their CDN solution is relies currently on a handful of servers which are located around the world, as illustrated below: Setting my Shift8 CDN account in WordPress In order to review Shift8 CDN, I installed it on my blog. To do that: Go to the Shift8 CDN webpage, create an account, fill out your wordpress site details. Then go back to your wordpress site -> Plugins and add Shift8 CDN. Copy the Shift8 CDN API key in there. You should see this picture as a proof of a successful integration: It is important to test the integration with the Test URL before enabling link, before activating the CDN. If you see the following image, it means there is an integration problem and you need to address your issue to the support through their forum or per email. I personally had ...