Arista Networks Leaf SSU Demo

Kamal Bakshi, Technical Marketing Engineer, demonstrates Arista Networks Leaf SSU, covering the latest resilience features of EOS for highly-available spine/leaf designs.

In this presentation at Networking Field Day 10, Kamal Bakshi showcased Arista Networks’ Leaf Stateful Switch Upgrade (SSU) capabilities by performing a live software upgrade on an Arista switch without disrupting ongoing traffic. The demonstration involved a video stream and continuous pings passing through a single-homed switch that was about to be reloaded. Despite rebooting the switch, including wiping and reloading its software image, the data plane remained fully operational with no interruptions to the video or packet loss, evidencing the effectiveness of the hitless upgrade process. This level of availability is achieved through Arista’s architecture that separates the control and data planes, allowing the switch hardware to continue forwarding traffic even when the control plane is temporarily down.

Bakshi delved into the technical underpinnings of Arista’s Extensible Operating System (EOS), highlighting that it runs on top of an unmodified Linux kernel with a Fedora-based user space. Within this environment, all network protocols and hardware drivers are implemented as user-space agents that interact with EOS’s SysDB, which holds the entire system state. During the hitless upgrade, the control processes were gracefully stopped, and the EOS image was fully replaced while the forwarding ASICs and TCAM continued to maintain network operations. Once the upgrade was complete, the agents restarted and repopulated SysDB by learning the switch state anew, enabling a seamless return of control functionality without affecting data traffic.

The demonstration emphasized Arista’s modular and resilient switch architecture, enabling highly available networks that can undergo significant maintenance like OS reboots without traffic disruption. The hitless upgrade process includes pre-upgrade validation, image verification, and ensures full compatibility before proceeding, making it a safe and efficient mechanism. Bakshi also noted the flexibility to upgrade individual processes, such as STP, independently if needed. Through capabilities like NSF for BGP and intelligent hardware/software separation, Arista’s switches support both Layer 2 and Layer 3 resiliency. This validates their suitability for high-availability spine/leaf designs commonly used in data centers and large-scale network environments.