Telstra chief executive Andy Penn says a major restructure at the company has been done to position it to buy the national broadband network in future, as investors backed his plans and welcomed moves to target new revenue in energy and health.

Shares in the telecommunications giant closed up three per cent at $3.08 on Thursday, after it used its annual investor day to show investors future options for cashing in on its infrastructure assets, such as mobile towers, and preserving its highly-prized dividend.