Category: Cumulus Linux

Cumulus Linux NVUE: an Incomplete Data Model

A few weeks ago I described how Cumulus Linux tried to put lipstick on a pig reduce the Linux data plane configuration pains with Network Command Line Utility. NCLU is a thin shim that takes CLI arguments, translates them into FRR or ifupdown configuration syntax, and updates the configuration files (similar to what Ansible is doing with something_config modules).

Obviously that wasn’t good enough. Cumulus Linux 4.4 introduced NVIDIA User Experience1 – a full-blown configuration engine with its own data model and REST API2.

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Cumulus Linux Network Command Line Utility (NCLU)

While ranting about Linux data plane configuration, I mentioned an interesting solution: Cumulus Linux Network Command Line Utility (NCLU), an attempt to make Linux networking more palatable to more traditional networking engineers.

NCLU is a simple wrapper around ifupdown2 and frr packages. You can execute net add and net del commands to set or remove configuration parameters1, and NCLU translates those commands into changes to corresponding configuration files.

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Video: Simplify Device Configurations with Cumulus Linux

The designers of Cumulus Linux CLI were always focused on simplifying network device configurations. One of the first features along these lines was BGP across unnumbered interfaces, then they introduced simplified EVPN configurations, and recently auto-MLAG and auto-BGP.

You can watch a short description of these features by Dinesh Dutt and Pete Lumbis in Simplify Network Configuration with Cumulus Linux and Smart Datacenter Defaults videos (part of Cumulus Linux section of Data Center Fabrics webinar).

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Auto-MLAG and Auto-BGP in Cumulus Linux

When I first met Cumulus Networks engineers (during NFD9) their focus on simplifying switch configurations totally delighted me (video).

I was ranting about the more traditional approach to data center fabric configuration resulting in dozens if not hundreds of device configuration commands in 2013… and other vendors still haven't done much in this respect in the meantime.

After solving the BGP configuration challenge (could you imagine configuring BGP in a leaf-and-spine fabric with just a few commands in 2015), they did the same thing with EVPN configuration, where they decided to implement the simplest possible design (EBGP-only fabric running EBGP EVPN sessions on leaf-to-spine links), resulting in another round of configuration simplicity.

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Packet Forwarding on Linux on Software Gone Wild

Linux operating system is used as the foundation for numerous network operating systems including Arista EOS and Cumulus Linux. It provides most networking constructs we grew familiar with including interfaces, VLANs, routing tables, VRFs and contexts, but they behave slightly differently from what we’re used to.

In Software Gone Wild Episode 86 Roopa Prabhu and David Ahern explained the fundamentals of packet forwarding on Linux, and the differences between Linux and more traditional network operating systems.

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And This Is Why Relying on Linux Makes Sense

Most networking operating systems include a mechanism to roll back device configuration and/or create configuration snapshots. These mechanisms usually work only for the device configuration, but do not include operating system images or other components (example: crypto keys).

Now imagine using RFC 1925 rule 6a and changing the “configuration rollback” problem into “file system snapshot” problem. That’s exactly what Cumulus Linux does in its newest release. Does it make sense? It depends.

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Dell OS10 and Cumulus Linux

A few days ago Dell announced their next-generation network OS based on Debian Linux, and bloggers (like my good friend Tom Hollingsworth) started wondering what’s going to happen with Cumulus Linux.

Let’s get into prognostication mode…

On a totally unrelated note, I love the picture Dell marketing put on the OS10 page. Linux distro in a binder? Really? When was the last time they checked the calendar?
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Cumulus Linux Base Technologies

Dinesh Dutt started his part of the Data Center Fabrics Update webinar with “what is Cumulus Linux all about” and “what data center architectures does it support” and then quickly jumped into details about the base technologies used by Cumulus Linux: MLAG and IP routing.

Not surprisingly, the MLAG part generated tons of questions, and Dinesh answered all of them, even when he had to say “We don’t do that.”

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Layer-3-Only Data Center Networks with Cumulus Linux on Software Gone Wild

With the advent of layer-3 leaf-and-spine data center fabrics, it became (almost) possible to build pure layer-3-only data center networks… if only the networking vendors would do the very last step and make every server-to-ToR interface a layer-3 interface. Cumulus decided to do just that.

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