Andy Bechtolsheim, Sun Microsystems' chief server architect and one of its founders, is leaving the company -- again -- to focus on a startup he founded, Arista Networks, that produces a high-speed Ethernet switch.

And he's stolen a senior VP from his larger and better-financed competitor, Cisco. Jayshree Ullal will become president and CEO and said she was leaving Cisco for Arista because it's "at the brink of pioneering new models for cloud networking," she said in a blog posted to the Arista Web site Wednesday. She also cited her 20-year working relationship with Bechtolsheim.

Bechtolsheim's movements are tracked closely in the Silicon Valley because they tend to mirror where the action is. He's also one of the few technologists who has had a repeat Midas touch. As a graduate student at Stanford, he got impatient waiting for central computing services and invented a local computer running Unix -- a workstation. Hence, he became employee No. 1 at Sun, ahead even of co-founders Scott McNealy, Vinod Khosla, and Bill Joy.

The 10 Gigabit Ethernet switch is such an obvious next step over the 1-Gb devices that now predominate that you'd wonder why Bechtolsheim is moving in that direction. Woven Systems, just down the road in Santa Clara, Calif., from his own Palo Alto startup, has been producing 10 Gigabit switches since March 2007. But Arista will offer its switch in a tight 1U package that will fit at the top of a stack of rack-mount servers or blades.

Bechtolsheim is doing for Arista what he did for Sun when he went back to the company in 2004. Sun had just acquired his company, Kealia, and Bechtolsheim showed Sun how it could get its sputtering x86 server business off the ground by focusing on AMD's hot Opteron chip. Sun produced two- and four-way Opteron servers and a giant Opteron-based storage server, called Thumper, which immediately enjoyed a measure of success. Arista puts 10 Gigabit Ethernet into a tight package and sells it not only as a way to connect rack-mount servers, but as a way of creating enterprise cloud computing centers. But it's not just betting on hardware packaging. Bechtolsheim is a full systems designer and pushes on the software front as well.

Cisco switches and routers dominate the industry and the Internet, but Bechtolsheim points out in talks and interviews that they are run by monolithic software systems, with as many as 20 million lines of code. Arista is staking its reputation on an Extensible Operating System. If it succeeds, Arista might become an acquisition target for Cisco or some other large networking equipment supplier, as Bechtolsheim well knows. His firm, Granite Systems, founded in 1995, was acquired by Cisco in 1996 for $220 million, and Bechtolsheim became head of what would eventually become Cisco's Catalyst product line.

Bechtolsheim was reported to be an early investor in Google, writing out a check on his front steps to "Google Inc." for Larry Page and Sergey Brin for $100,000 as he left for work one morning. The pair hadn't formed a company yet and had no account in which to deposit it. Bechtolsheim confirmed the story in an interview with InformationWeek as he returned to Sun in 2004, saying he recognized immediately that Google was using Internet searches to generate a page-ranking metric, an innovation that he was sure would have a large impact.

Bechtolsheim shows up on the Forbes list of the 691 richest people in the world, ranking 620th and reportedly having a net worth of $1 billion.

He co-founded and co-funds Arista with Stanford professor David Cheriton, a longtime associate, who will serve as its chief scientist. At a panel during VMworld in Los Angeles in 2007, Cheriton asserted that software engineers needed to think more like aeronautical engineers. Once their systems are up and running, they need to keep running, he said.

Arista is giving its switches a version of the Linux operating system that it calls Extensible Operating System. While Linux is heavily modularized, Arista is taking the concept a step further by separating the network state from the switch CPU processing state. It allows greater isolation of independent processes and isolates any system fault to a single module of the operating system. The approach also allows modules to be updated while the system is running without disrupting operations, according to an EOS white paper on Arista's Web site.