The activist hedge fund Jana Partners has set its sights on Juniper Networks, calling on the networking company to tighten its belt and give more money back to shareholders.

Citing fresh opportunities with a new leader at the helm of Juniper, Jana told investors it took a large stake in the company, according to its year-end letter sent to investors on Thursday evening and reviewed by DealBook.

The move is likely to bolster another campaign to change the company started by the hedge fund Elliott Management just one week ago. Elliott, run by the billionaire investor Paul Singer, wants Juniper to cut costs, streamline its product offerings and return money to shareholders. It disclosed it has a 6.2 percent stake in Juniper, one of its biggest current activist positions.

Both hedge funds have expressed optimism that Juniper’s new chief executive, Shaygan Kheradpir, could help to bring about change at the company. Mr. Kheradpir, previously the chief technology officer at Barclays, took over as chief executive this month.

The change of guard represented a “chance to reframe the story,” someone familiar with Elliott’s thinking said last week, while Jana said in its letter to investors that it offered the “potential for a change of perspective and sense of urgency.”

Jana also accused Juniper of having an “unfocused product line up, a lazy balance sheet and share price underperformance.” Last week, Elliott characterized the underperformance of Juniper’s share price compared with its peers’ as “severe and consistent.”

For its part, Jana wants the company to divest itself of certain business lines and begin a “large” capital return program, calling its balance sheet “overcapitalized… even by Silicon Valley standards.” It estimated the company could save $300 million a year.

The company has $3 billion in net cash, or $6 a share, Jana said.

In a sign that the activist hedge fund could begin to apply pressure to Juniper’s board, the hedge told its investors, “we believe the board would benefit from the addition of new directors with a fresh perspective.”