Avaya CEO Lou D'Ambrosio has stepped down for unspecified medical reasons and is being replaced temporarily by former Cisco chief development officer Charles Giancarlo, most recently the managing director of Silver Lake Partners, a private equity firm that is co-owner of Avaya.

Giancarlo says he has no plans to stay on permanently at Avaya, which is in the midst of reinventing itself as a software and services company as opposed to a pure telephony-systems vendor.

While Avaya still makes phones and PBXs, it increasingly is selling them bundled with software peripherals and support services crafted for specific classes of users. The thrust relies on partnerships with Cisco, IBM and Microsoft.

Such packages include systems that link stores' customers to knowledgeable employees for information about products while they are shopping. Another application is a videoconferencing system that brings translators to emergency rooms to help diagnoses.

D'Ambrosio had been with Avaya for six years, two as CEO, and it was under his leadership that the company was taken private by Silver Lake Partners and TPG. Since then he has been working on making it more efficient.

The company would not offer details about D'Ambrosio's medical condition.

Giancarlo at one time was seen as next in line to replace Cisco CEO John Chambers when he chooses to retire. When Giancarlo left Cisco at the end of 2007, Chambers said Cisco was not expecting his departure and it was unprepared for his leaving.