SDN in action: Hands-on with Cumulus Linux

Imagine being able to manage scores of network switches as easily as scores of servers; Cumulus Linux makes it happen

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The stage is set for SDN (software-defined networking) to change the way we push data through our infrastructures, with the promises of more agile network provisioning and management, as well as more affordable network hardware. But for many, the SDN concept is still amorphous. What does SDN look like in practice? 

To shed light on this question, I sat down with a few Dell Networking S6000 switches running Cumulus Linux 2.2.1. There are many approaches to an SDN solution, but one of the most significant is the advent of white-box switches and à la carte switch firmware. This is the essence of the solution offered by Cumulus Networks.

Decidedly Debian

Cumulus Linux is based on the Debian distribution. You may be SSHing into a 1U box with 52 physical interfaces, but from the inside, a Cumulus Networks switch is like any other Linux box. I ran switches built on a Freescale PowerPC base with 2GB of RAM and a 394MB read-write overlay root partition with 390MB free, or what you might expect from a small but complete Linux system.

As with any other Debian Linux box, if you want to configure an Ethernet interface, you either do it from the shell prompt with the various ip tools, or add an entry to the /etc/network/interfaces file that provides details about that physical interface, then use ifup/ifdown to control the interface. If you know how to do standard bridging, routing, forwarding, and firewalling with Debian, then you know how to configure Cumulus Linux for those tasks -- there is no real learning curve.

Cumulus makes use of Quagga for advanced routing protocols like OSPF and BGP; if you’ve used Quagga, you’ll be in familiar territory. Further, Quagga offers a Cisco-like interface that will make veteran Cisco admins feel right at home.

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