Scott Emery

Author Archives: Scott Emery

Is It Real, or Is It Cumulus VX?

Phew! Cumulus Linux 3.0 has just been released! A big shout out to all of my engineering colleagues who worked so hard to make this happen. JR Rivers gave an overview of all the goodies included in 3.0 in his recent blog post. Stay tuned for more blog posts from other engineers for details on all of those new features.

But Cumulus Linux isn’t the only beneficiary of all the 3.0 work. Cumulus VX, our free virtual machine-based version of Cumulus Linux, also has some pretty cool new tricks. When we launched Cumulus VX last August we thought it would be a way for people to get hands on with a Linux-based switch operating system, in their own environment and without any commitment. Boy, Were we surprised at how it quickly became so much more. With over 3,800 unique users, Cumulus VX is being deployed in all sorts of ways we never dreamed of. As just one example, existing customers are using it to validate their configurations before upgrading their physical switches from one release to another.

What’s New?


And that brings me to the first change we’ve made: concurrent releases. Our plan from now on Continue reading

MLAG – An Implementation for Everyone!

I typically don’t to get up on a soapbox and preach the awesomeness of Linux networking, but I think I’m going to make an exception for this one topic: MLAG.

Yes, MLAG, that wonderful non-standard Multi-chassis Link Aggregation protocol that enables layer 2 multipathing from the host to gain either additional bandwidth or link resiliency. Every vendor that supports MLAG does so by using their own custom rolled implementation of it, which means Vendor A’s version of MLAG cannot interoperate with Vendor B’s version of MLAG. So I can’t have one switch be an “X” box and another be a “Y” box and expect the two to be part of the same MLAG configuration with a Dell server.

That ends today (arguably I could have said, that ended January 2015 when Cumulus Networks shipped with MLAG support in Cumulus Linux 2.5, but I’ll get to that in a bit).  Several weeks ago I was with my colleagues Shrijeet Mukherjee and Tuyen Quoc giving a talk about how “Linux Networking Is Awesome” at the 2016 OCP Summit. During our standing room only talk, we explained how Linux networking has become the de-facto networking stack in the data center (and Continue reading

Host-MLAG: Don’t Let a Switch Bring Down Your Servers

How do you protect against failures in a data center? Selecting a stable location and using quality equipment is a good start.

But no matter how much you spend and how lofty the promises of the vendor, hardware does fail. And because systems do inevitably fail, redundancy is your friend when it comes to minimizing the impact of a failure. Systems have redundant power supplies and fans. The connections between systems are redundant. The systems themselves are redundant. And in some cases entire data centers are redundant in different geographical locations.

With the release of Cumulus Linux 2.2, there is now an open solution for redundant layer 2 top of rack, or ToR, switches. No longer will a single ToR switch failure take out your entire rack of servers. This is because Cumulus Linux 2.2 includes Host-MLAG, which allows servers to connect to redundant ToR switches using active-active LACP bonding. Some of the advantages of Host-MLAG include:

  • Unlike a single ToR solution, with Host-MLAG, the failure of one ToR switch still provides full connectivity to all of the servers.
  • With active-active connections to the ToRs, the bandwidth to and from the servers is doubled.
  • Host-MLAG requires no special Continue reading