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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 ...