The most interesting aspect of Cumulus Networks’ latest operating system update, which was released today, might be the feature that's not fully available yet.

Included in the announcement of Cumulus Linux 3.2 is a "coming soon" mention of Ethernet virtual private networks (EVPNs). An IETF standard, EVPNs have emerged as a way to get network overlays to scale.

Incumbent switch vendors have already been supported EVPNs — Arista, Cisco, and Juniper included. And to be fair, Cumulus Linux 3.1.1 included EVPNs as a preview feature for switches based on Broadcom chips.

Network virtualization typically uses the Layer 2 VXLAN protocol to create overlay connections. But Layer 2 has scaling limits. To get around those, VXLAN borrows from Layer 3 protocols.

EVPN uses a standard called multiprotocol BGP (MP-BGP) to carry this Layer 2/3 mixture of information. Using EVPN, a network owner can avoid using a controller. It's also a way to avoid a behavior called flooding, where a switch queries all its neighbors to find out which is the correct destination for a packet. Flooding is normal for Ethernet and VXLAN; it's just that MP-BGP provides a way to minimize it.

Other features in Cumulus Linux 3.2 include protocol-independent multicast (PIM) and a snapshot feature that lets operators roll back the software to a previous version, providing a way to recover from operator errors or experiments gone awry. (Admittedly, the rollback feature might interest operators a lot more than EVPNs do.)

Release 3.2 also marks general availability for the network command line utility (NCLU) that the company announced in November.