Sun Microsystems ( JAVA) shares slipped Thursday following news that co-founder and chief architect Andy Bechtolsheim will reduce his role to help build network switch startup Arista Networks.

The firm's beleaguered stock fell 18 cents to $4.54 in recent trading, in early trading, well below its 52-week high of $23.08.

Arista issued a statement confirming Bechtolsheim's appointment as its chairman and chief development officer, although Sun still listed him as its chief architect on the company's Web site early Thursday.

A Sun spokeswoman confirmed that Bechtolsheim will continue to work part-time for the company. "Andy will remain with Sun to continue his present involvement with the Sun Systems group in helping to drive new product architectures, including X64 servers and storage servers, and will continue to work on key strategic initiatives such as High Performance Computing," she wrote, in an email to TheStreet.com

Bechtolsheim co-founded Sun in 1982 with Scott McNealy, Vinod Khosla, and Bill Joy, and was the driving force behind the company's workstation and network server strategies. The shifting focus of one of its key technology experts nonetheless comes at a difficult time for Sun, which is wrestling with falling sales and a tough spending climate.

Sun offered disappointing preliminary first-quarter results Monday, amid a tech spending slowdown and stiff completion from the likes of IBM ( IBM) and Hewlett-Packard ( HPQ). The company is also in the throes of a major restructuring effort which it hopes will boost its profit.

Bechtolsheim's appointment as Arista's chief development officer, however, did not come completely out of the blue. He is one of the startup's co-founders, and also has a strong background in network switch technology.

Arista is touting high-speed 10-Gigabit Ethernet switches and is clearly aiming to challenge Cisco ( CSCO ) in the datacenter networking niche. The startup is also eyeing the opportunities presented by "cloud" computing, where firms offer a range of technology services via the Internet.

Bechtolsheim's Arista move is not the first time that he has looked for opportunities outside of Sun. He left the technology giant in 1995 to found Granite Systems, a a company that was acquired by Cisco the following year. Bechtolsheim subsequently became Cisco's vice president of engineering and later general manager of the firm's Gigabit Systems business, which developed the popular Catalyst 4000 switch.

He rejoined Sun in 2004 when it acquired Kealia, a server startup that Bechtolsheim co-founded with his long-time collaborator David Cheriton, a Stanford University professor Cheriton whoalso helped found Arista, and serves as the startup's chief scientist.

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