Author: David Varnum


Becoming an AWS Certified Solutions Architect Associate

Architecting for the cloud is becoming a highly desired skill set. Working as a consultant, I’m often in situations where clients are overwhelmed with questions about the cloud. How do I migrate my applications? How do I secure everything? How does it integrate with LDAP and DNS? What’s the best way to connect to the cloud? Will I need to rewrite my applications? How do I manage costs? While some of these vague questions can be answered with regurgitated marketing material, I feel a sense of duty to understand and explain these concepts at a deeper level. Some clients I work with already have a significant presence in the Cloud. Other clients have various pools of cloud resources and are looking to rationalize or provide a strategy around optimizing the sprawling resources. Because of recent exposure to cloud over the past couple of years, and due to the demand for practical knowledge of cloud architecture, a rigorous education program became an obvious next step for my career.  At the beginning of 2019, I made a goal to become an AWS Certified Solutions Architect Associate. As of May 3rd, 2019 – that goal is achieved!


Arista BGP EVPN – Ansible Lab

In the previous two blog posts, I covered the concepts of EVPN and shared a detailed configuration example on Arista EOS. In this blog post, I’ll be covering how to automate the deployment of EVPN in a lab environment. After deployment, I want to run validations to make sure my intent is being met. Lastly, I’ll play around with a few scripts to deploy L2 and L3 VXLAN services. 

When studying this technology and demonstrating it to clients, I chose to use GNS3 because it’s nice to visualize the topology, easily perform packet captures, and I can share the project file with fellow co-workers using a GNS3 Server. I could have chosen Vagrant for this, but since my topology has 10 vEOS devices, I found the boot time to be too long (although I hear if I use KVM I can boot the nodes in parallel). I chose 8 leafs because it gave me the most flexibility to demonstrate VXLAN Bridging, VLAN Routing, Border Services (such as segmentation or traffic engineering), and so on. You could probably get away with fewer leafs depending on your preference. That said, my topology in GNS3 looks like this:

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Arista BGP EVPN – Configuration Example

This is a follow-up to my previous article, Arista BGP EVPN Overiew and Concepts. In the previous article, I discussed some terminologies and behavior of EVPN and the reason why EVPN is valuable in Data Center and Campus networks. Since then, I’ve learned how valuable it is in Service Provider networks as well, but I’ll save that for another day. In this article, I want to walk through a configuration example.

In this topology, we have 2 Spines and 8 Leafs. Each pair of Leafs will form a VXLAN Tunnel Endpoint (VTEP). We will start with the initial configuration of underlay components, such as MLAG and underlay BGP. Next, we’ll configure the EVPN overlay and VTEPs. Lastly, I’ll give an example configuration of L2VXLAN (EVPN Type-2) and L3VXLAN (EVPN Type-5). While most of this configuration will function in production networks, I highly advise first building something out virtually to do testing (GNS3, Vagrant, what-have-you). I won’t be covering special use cases or every possible configuration parameter, but hopefully this is a good start to get you going on to super deep dives.

I’ll have a complete configuration workbook attached at the end of this blog.

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Arista BGP EVPN – Overview and Concepts


Traditionally, Data Centers used lots of Layer 2 links that spanned entire racks, rows, cages, floors, for as far as the eye could see. These large L2 domains were not ideal for a data center, due to the slow convergence, unnecessary broadcasts, and difficulty in administering. To optimize the data center network, we needed to reduce the use of and reliance on layer 2 protocols such as Spanning Tree. The challenge, however, is the fact that Data Centers need Layer 2 stretching from rack to rack, row to row, sometimes from data center to data center, not only for application requirements but also for fault tolerance and workload mobility. Numerous technologies have come forth to battle this limitation, such as TRILL, FabricPath, and VXLAN. Of these three, it is Virtual Extensible LAN (VXLAN) that has seen rapid adoption in modern data centers. (more…)

Leveraging SD-WAN for Mergers & Acquisitions

A colleague recently asked me if SD-WAN could be leveraged to expedite network integration as a result of a merger or acquisition. His thoughts were that this could potentially provide a means to securely integration networks in a short amount of time.  At first I thought this made no sense — SD-WAN is not related to this challenge whatsoever. However, the idea stuck in my head like a bad catchy tune. I started thinking… maybe in certain circumstances this could work?  This post is a collection of some ideas I’ve been brewing with respect to the secure and timely integration of disparate networks using over-the-counter SD-WAN. (more…)