Category Archives for "Cumulus Networks Blog"

Lessons learned from Black Friday and Cyber Monday


If you’re a consumer-facing business, Black Friday and Cyber Monday are the D-Day for IT operations. Low-level estimates indicate that upwards of 20% of all revenues for companies can occur within these two days. The stakes are even higher if you’re a payment processor as you aggregate the purchases across all consumer businesses. This means that the need to remain available during these crucial 96 hours is paramount.

My colleague, David, and I have been working the past 10 months preparing for this day.  In January 2018 we started a new deployment with a large payment processor to help them build out capacity for their projected 2018 holiday payment growth. Our goal was to create a brand new, 11 rack data center to create a third region to supplement the existing two regions used for payment processing. In addition, we helped deploy additional Cumulus racks and capacity at the existing two regions, which were historically built with traditional vendors.

Now that both days have come and gone, read on to find out what we learned from this experience.

Server Interop Testing

Payment processing has most of its weight on the payment applications running in the data center. As with Continue reading

Cumulus Linux in the enterprise campus.

As most know, Cumulus Linux was originally intended for data center switching and routing but over the years, our customer base has requested that we expand into the enterprise campus feature set too. Slowly, we’ve done just that.

With this expansion though, there are a few items that IT managers tend to take for granted in an all Cisco environment that may need some extra attention when using Cumulus Linux as a campus switch. This is especially the case when it comes to IEEE 802.1x, desk phones, etc.

Most of the phones we inter-operate with have been of the Cisco variety and quite often, those phones are connected to Cisco switches. There are a few tweaks from the default Cumulus settings that need to be called out in this environment and we’ll now go over what those are and how you can tweek them.

Cisco IP Phones TLV change

Cisco IP phones may revert to a different VLAN after initial negotiation. One of our enterprise customers found that according to a Cisco tech note on LLDP-MED and CDP, CDP should be disabled on non-Cisco switches connecting to Cisco phones.

To eliminate this behavior, make the following adjustment to the Continue reading

Cumulus content roundup: November

We’re at it again with the Cumulus content roundup- November edition. As always, we’ve kept busy this month with lots of great resources and news for you to read. From EVPN Underlay Routing Protocol to the benefits of Layer 3, we’ve rounded it all up right here, so settle in and stay a while!

From Cumulus Networks:

Choosing an EVPN Underlay Routing Protocol: We take a look at the options in routing protocols that could use as an underlay with the objective of understanding what might make them a fit or not for deployment in an EVPN network.

The Benefits of Flexible Multi-Cloud and Multi-Region Networking: Here we explore some of the reasons multi-cloud is fantastic for enterprises when they consider security, flexibility, reliability, and cost-effectiveness.

Cumulus Linux Automation with Standard Linux Tooling: This blog focuses on the different options available for modern automation, & how the Cumulus Linux approach provides the greatest amount of flexibility.

Cumulus Networks Open-Ended NCLU Net Example Command: NCLU is the always helpful Network Command Line Utility and supports both inspection and modification of Cumulus Networks configuration data.

Layer 3 can do it better. I’m convinced. You should be too.: Are you bringing the best solution Continue reading

Layer 3 can do it better. I’m convinced. You should be too.

There are lots of reasons why we have a tendency to stick to what we know best, but when new solutions present themselves, as the decision makers, we have to make sure we’re still bringing the best solution to our business and our customers. This post will highlight the virtues of building an IP based fabric of point to point routed links arranged in a Clos spine and leaf topology and why it is superior to legacy layer 2 hierarchical designs in the data center.

It’s not only possible, but far easier to build, maintain and operate a pure IP based fabric than you might think. The secret is that by pushing layer 2 broadcast domains as far out to the edges as possible, the data center network can be simpler, more reliable and easier to scale. For context, consider the existing layer 2 hierarchical model illustrated below:

This design depends heavily on MLAG. The peer link is compulsory between two switches providing an MLAG. An individual link failure on the peer link would be more consequential than any of the other links. Ideally, we try to avoid linchpin situations like this. This design does provide redundancy, but depending on Continue reading

Cumulus Networks Open-Ended NCLU Net Example Command

NCLU is the always helpful Network Command Line Utility. It’s a command interface for our products and platforms that’s designed to provide direct, simple access to network configuration information. Thus, NCLU supports both inspection and modification of Cumulus Networks configuration data. Better yet, NCLU is easy to customize for local environments and naming conventions using its net example facility.

NCLU Overview

In general, NCLU enables users at the command line to learn about current configurations, and make changes or additions to such configurations. NCLU reports on Interfaces and can provide information about IP addresses, VLANs, Access controls, Trunking, STP, and more. At the routing level, NCLU provides information about Border Gateway Protocol (BGP) and Open Shortest Path First (OSPF) routing protocol settings and configurations. NCLU also offers information about services, including hostnames, NTP (Network Time Protocol), Timezone, and so on.

NCLU also includes comprehensive, context-sensitive help. Starting with the basic net command, users can learn about the various sub-commands available to them. Similarly, entering net <sub-command-name> provides help for that specific sub-command. This is how Cumulus (and other forms of) Linux delivers help information for users of complex commands like net.

In addition, NCLU commands provide control over configuration staging, Continue reading

Cumulus Linux Automation with Standard Linux Tooling

One thing’s for sure: The world of networking and networking administration is quickly changing. Part of this change is an evolution from old-school, proprietary centralized networking to more open options. This evolution has several different effects on the way network designers, administrators and engineers design and operate the network. This blog will focus on the different options available for modern automation, and how the Cumulus Linux approach provides the greatest amount of flexibility.

Breaking the Stranglehold

It wasn’t too long ago that the few big networking vendors had an almost unbreakable grip on organizational networking implementations, and correspondingly, with the way these implementations were managed. For most, this included the configuration of the various types of networking equipment using a command-line interface (CLI) and proprietary commands. Automating these types of solutions most often required either an offering developed by the vendors themselves, or the use of an application programming interface (API) written to interface with their products.

The question is whether this was a good thing or not. Generally, vendor-specific solutions have their advantages because they’re able to interface closely with the specific device code and take advantage of communications between the device coding team and the tools coding team.

Continue reading

Choosing an EVPN Underlay Routing Protocol

EVPN is all the rage these days. The ability to do L2 extension and L3 isolation over a single IP fabric is a cornerstone to building the next-generation of private clouds. BGP extensions spelled out in RFC 7432 and the addition of VxLAN in IETF draft-ietf-bess-evpn-overlay established VxLAN as the datacenter overlay encapsulation and BGP as the control plane from VxLAN endpoint (VTEP) to VxLAN endpoint. Although RFC 7938 tells us how to use BGP in the data center, it doesn’t discuss how it would behave with BGP as an overlay as well. As a result, every vendor seems to have their own ideas about how we should build the “underlay” network to get from VTEP to VTEP, allowing BGP-EVPN to run over the top.

An example of a single leaf’s BGP peering for EVPN connectivity from VTEP to VTEP

Let’s take a look at our options in routing protocols we could use as an underlay and understand their strengths and weaknesses that make them a good or bad fit for deployment in an EVPN network. We’ll go through IS-IS, OSPF, iBGP and eBGP. I won’t discuss EIGRP. Although it’s now an IETF standard, it’s still not widely supported Continue reading

Cumulus content roundup: October

.We’re back with the Cumulus content roundup- October edition. We’ve kept busy this month with a new white boarding video series, podcasts, resources and more. Covering everything from Open Source to digital transformation, we’ve rounded it all up right here, so settle in and stay a while!

From Cumulus Networks:

Preparing your network for digital transformation: Learn about the primary challenges with digital transformation and how web-scale networking principles make digital transformation possible and profitable. Is your network ready for the future?

Web-scale networking for cloud service providers: Find out why cloud service providers need to have agile, highly scalable and cost effective infrastructure in order to stand out to their customers.

Our dedicated approach to open source networking: Read our philosophy and how we’ve contributed to and participated in the open source community.

Web-scale Whiteboarding: Openstack Overview: Watch our brand new series of whiteboarding videos with our very own Pete Lumbis

Kernel of Truth: Episode 9: Tune into this podcast episode as we dive into Layer 3 networking and why we believe it’s the future of network design.

News from the web:

Gartner Peer Insights: See the full list of companies recognized for Best Data Networking of 2018, including Cumulus Networks!

Continue reading

Use Cumulus HTTP API to Help Automate Common Network Tasks

Cumulus Linux includes a RESTful programming interface for accessing network devices running that OS. It’s called HTTP API, and it implements an API to access the OpenStack ML2 driver and Network Command Line Utility, or NCLU. Understanding exactly what this means, and how it works, is essential before digging into the possibilities it presents. Here’s an overview to get this going.

The OpenStack ML2 Driver

The ML2 Driver, a.k.a. (in OpenStack’s terms) the Modular Layer 2 neutron plug-in, provides a framework. It enables OpenStack-based networking to use a variety of Layer 2 networking technologies, including those from Cumulus (for which a specific ML2 driver is available and ready to use). To use the OpenStack ML2 driver with Cumulus Linux switches, two essential ingredients must be present:

  1. The REST API, which comes installed in Cumulus Linux. This includes an ML2 HTTP Server, which recognizes and responds to such requests. This runs on Cumulus-based network nodes to which management consoles or nodes will attach to interrogate, configure, or otherwise interact underlying devices.
  2.  Elsewhere on the network, the Cumulus ML2 Mechanism Driver should be installed on a VM or system running Cumulus Linux. This is called a “controller node.” Continue reading

BGP Unnumbered Overview

The Border Gateway Protocol (BGP) is an IP reachability protocol that you can use to exchange IP prefixes. Traditionally, one of the nuisances of configuring BGP is that if you want to exchange IPv4 prefixes you have to configure an IPv4 address for each BGP peer. In a large network, this can consume a lot of your address space, requiring a separate IP address for each peer-facing interface.

BGP Over IPv4 Interfaces

To understand where BGP unnumbered fits in, it helps to understand how BGP has historically worked over IPv4. Peers connect via IPv4 over TCP port 179. Once they’ve established a session, they exchange prefixes. When a BGP peer advertises an IPv4 prefix, it must include an IPv4 next hop address, which is usually the address of the advertising router. This requires, of course, that each BGP peer has an IPv4 address.

As a simple example, using the Cumulus Reference Topology, let’s configure BGP peerings as follows:

Between spine01 (AS 65020, and leaf01 (AS 65011,

Between spine01 ( and leaf02 (AS 65012,

Leaf01 will advertise the prefix and leaf02 will Continue reading

7 Guiding Principles for Leading Data Center Networks

Whether you’re starting out on a fresh playing field or diving into a mud pool of decades-old complexity, designing and deploying a new or modernized data center is a rewarding endeavor; not just for the engineers and architects, but also for the businesses that reap the benefits of agility, scalability, and performance that come along with it.

And the first step on that road is to talk. The initial conversations with thought leaders, business strategists, and technical architects are the most pivotal in the discovery phase of any large project. It is at this phase that the box is forming, and questions must be asked outside of it to shape its dimensions. To transform the network, you must be prepared to ask challenging questions that drive conversations around open networking, automation, modularity, scalability, segmentation and re-usability. Before vendor selection, it is essential to compile a list of business and technical requirements founded upon a set of guiding principles.

Here are seven to keep in your pocket:
1. The network architecture should use standards-based protocols and services
2. The network should be serviceable without downtime
3. The network architecture should promote automation
4. The network should be consumable
5. Physical boundaries Continue reading

The Benefits of Flexible Multi-Cloud and Multi-Region Networking

A report recently published by 451 Research shows that almost 70% of all enterprises will be using a multi-cloud or hybrid IT infrastructure in a year’s time. As more and more enterprises are swayed into the cloud, companies who have already adopted the cloud are now choosing to go with multi-cloud infrastructure or hybrid architecture for their IT requirements.

The report also showcased that about 60% of all workloads are expected to run using a form of hosted cloud service by 2019. This is an increase of about 45% from 2017. This marks an impressive change from DIY owned and operated services to a cloud or third-party hosted IT services. Therefore, the future of IT services is clearly hybrid and multi-cloud.

Here we explore some of the reasons multi-cloud is a fantastic idea for enterprises when they consider security, flexibility, reliability, and cost-effectiveness.

Reduce Security Risks Like a DDoS Attack

A Distributed Denial of Service or DDoS attack is when a number of different computer systems attack a server, website, network resource or a cloud hosting unit. A DDoS attack can be executed by an individual as well as a federal government.

In a scenario that your company’s website is Continue reading

Kernel of Truth episode 9: Layer 3 Networking

Click  here for our previous episode.

For this week’s Kernel of Truth podcast we dive into Layer 3 networking and why we believe it’s the future of network design. In this episode we cover everything about why you should transition to Layer 3, how to make that transition, and why L3 is different than Layer 2. We bring in Jason Heller, a Principle Consulting Architect here at Cumulus, as well as Donald Sharp, a Principle Engineer to gain insight into the future of Layer 3 and the possibilities it can hold for you.

Tune in to to hear the pros and cons of L3 and the best way to begin transitioning and the options that come with Layer 3 networking. If you like what you hear on this week’s episode make sure to follow and subscribe!

Guest Bios

Brian O’Sullivan: Brian O’Sullivan is a generalist who happened to end up in a highly specialized field through no fault of his own. For 15 or so years he’s held software Product Management positions at Juniper Networks as well as other smaller companies. Once he Continue reading

NetQ agent on a host

We all know and love NetQ – it works hand-in-hand with Linux to accelerate data center operations. Customers love how easy it is to install and operate which makes their lives easier. Also, it can prevent and find issues in a data center by viewing the entire data center as a whole and providing three different types of services:

  • Preventative: NetQ allows an engineer to check all data center configurations and state in a few steps from any location in the network. The validation can be done on a virtual network using vagrant with Cumulus VX or if a virtual environment is not available, it can also be used during an change outage window. Since NetQ has built in analyzers of the network as a whole, no scripting is required and the validation is done from one location, rather than hop by hop. It can also shorten outage windows needed for network changes allowing shorter outage windows virtually or during outage windows.
  • Proactive: NetQ supplies notifications if something goes wrong in the network by either logging it to a file or integrating with third party applications like Slack, PagerDuty, or Splunk. It can also be filtered to ensure the right Continue reading

Announcement: Cumulus recognized by both our employees & customers

It’s not every day you get recognized. But to get recognized TWICE in one day? Now that’s a rare experience. We’re thrilled to announce that Cumulus Networks has been recognized with both the FORTUNE 2018 50 Best Small and 100 Medium Size Companies to Work For award, as well as  Gartner Customers’ Choice for Data Center Networking.

With recognition like this, we’re taking time to celebrate and appreciate the awesome and talented people we get to work with every day.

Cumulus awarded as a FORTUNE 2018 50 Best Small and 100 Medium Size Companies to Work For

The Fortune award is one of the most prestigious and for good reason — Their rigorous methodology focuses on more than just benefits and office snacks. According to their 2017 methodology statement:

All employees were invited to participate in the survey, which is designed to reveal whether the organization is consistently a great place to work for all its people. Meaning: Do employees trust the people they work for? Are they treated fairly and with respect? Are people proud of their work? Do they enjoy the folks they work with? Are great experiences available to everyone – or does it Continue reading

Comparing Upgrade Strategies with Cumulus Linux

You’ve been running your Cumulus Linux network for a while, and everything has been running perfectly. Cumulus Linux has sliced your bread, you’ve gotten a promotion because your boss can’t believe how successful the project was, and the cost savings being felt by the organization. Your company has even been able to fire the accountant because Cumulus Linux has surprisingly also done your taxes for the coming year, and in general everything is going swimmingly with your open networking.

So what now, is our story over? Well not exactly, enterprise networks have long lifespans. Hyperscalers typically operate on a refresh cycle of 3-5 years. For them, anything over 3/yrs old is considered tech debt. Anything over 5/yrs old is considered a critical fault point. Your typical enterprise network may be around even longer than that. It is very common in this timespan for the needs of the applications to change requiring the network to change too. This often requires support for newer features at some point in the lifecycle of the equipment.

While the scenario above is quite rosey, (Hey – this is our blog after all!) the reasons for wanting to upgrade are many and varied. New features, Continue reading

Open Switch Hardware’s Journey into the Linux and Kernel Community

You have read, heard and seen us talk about the benefits of Linux, open source and community. Here, here, and here… and I am pretty sure everywhere. This blog walks you through our journey of pushing Linux open switch ASICs into the Linux kernel and ecosystem. Before we begin, let me tell you that it has and continues to be a fun ride!


A quick historical recap on Linux networking

The Linux kernel has been doing network hardware offloads and acceleration for decades (Nics, smart-nics, wireless AP’s and many other places). Because of this, the kernel has had the infrastructure and the right abstractions to recognize and register a networking hardware device for decades. And this infrastructure has matured over time.

For hardware vendors, enabling their networking hardware for Linux just made it easier to take their hardware to new customers, objectives and industries. Today Linux enablement is the best way to get faster adoption of your hardware or faster marketing for your hardware. It has become a norm for hardware vendors to get their hardware ready for Linux first: getting their drivers in the upstream kernel and getting hardware tools ready for the Linux ecosystem.

Continue reading

Salt Use Cases for Cumulus Linux

A talking point I often lean on when speaking to customers is, “It’s Linux, so use whatever tool you like.” This approach can be especially paralyzing for customers that are just getting started with automating their network and compute infrastructure in a uniform way. In those particular situations, diving into the numerous articles that pit the various automation tools against each other can be counterproductive. Instead, I often find the most value in looking at a few examples of a particular tool in action that is addressing a use case which is relevant to me, while following along hands-on.

Salt frequently comes up as one of the options in the infrastructure configuration management conversation, however its main differentiator is the message bus architecture and the ability to react to events in real time. While that sounds a bit abstract, the main question we should be asking ourselves is how will this simplify the day to day management of my infrastructure? In this post, we’ll step through getting the configuration on a couple Cumulus switches under full management with Salt, and end with a practical event-based workflow for adding and replacing devices in our infrastructure.

Configuration Management

In a previous Continue reading

Kernel of Truth episode 8: Network agility

Subscribe to Kernel of Truth on iTunes, Google Play, Spotify, Castbox and Stitcher!

Click here for our previous episode.

On this week’s Kernel of Truth episode, we’re breaking down network agility and why it’s important to you. The networking world loves a good acronym, but have no fear, this episode will also begin to unscramble the alphabet soup that comes with the technology. For this episode we brought in Attilla de Groot and Scott Edwards to discuss why agile networks are changing the tech world, how we got here, and what’s next.

If you’re interested in learning about the virtualization of IT, new innovations, and how that’s helping computing power become greater and faster than ever, this episode is for you. We discuss how Cumulus is making design methods and network architecture that’s easier for our customers to use and how we’re working to design a simpler, more freeing approach to networking and much more. So grab your headphones and sit back for 25 minutes of networking goodness!


Guest Bios

Attilla de Groot: Cumulus Networks; Attilla has spent the last 15 years at the cutting edge of Continue reading

A minimalist approach to network architecture

Minimalism, as a current concept, is not just about owning fewer things, or eliminating distractions, or consuming only specific coffees sold in unlabeled packaging at chairless coffee shops. Minimalism is a philosophical force and practical approach to life, that when applied correctly, can bring peace, happiness, and enrichment to your way of living. How do these core virtues of minimalism apply to network design? Read on. (And don’t worry, you can keep all of your stuff, your color TV and cell phones, and your roomy house, too – we’re just talking about networks here.)

Joshua Fields Millburn and Ryan Nicodemus, who founded, sacrificed their former careers to share the concept of minimalism all over the globe, helping more than 20 million people live more meaningful lives. They’ve grounded the concepts of minimalism into a practical and elegant foundation that fits nicely in a modern society. They defined what many believe to be the core virtues of minimalism, ideas to internalize on your journey through life. When it comes to network design, here are five core virtues that prove to be incredibly valuable:

• Reclaim your time
• Create more, consume less
• Contribute beyond yourself
• Experience Continue reading

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