The company, in a news release, says the resignation came “for matters regarding personal conduct” not related to F5 operations or financial condition.

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F5 Networks CEO Manny Rivelo, who was appointed in April, has resigned from the Seattle company, effective immediately.

In a news release Monday, the company said the resignation came “for matters regarding personal conduct” unrelated to the company’s operations or financials.

John McAdam, the long-serving CEO of F5 and Rivelo’s predecessor, will step back into the executive role as president and CEO. McAdam will stay until the company finds a permanent replacement for Rivelo.

McAdam, 64, retired earlier this year after 15 years at the helm of the company. Rivelo was F5’s vice president of strategic solutions. He joined the company in 2011 after 20 years at competitor Cisco.

A spokesman for F5 said he couldn’t share any other details of Rivelo’s unexpected departure.

McAdam became chairman of the board when he retired. He will now give up that role, and remain on the board as a member. Alan Higginson, now the board’s lead independent director, will become chairman.

“I want to emphasize that these actions are in no way related to the company’s operating performance or financial condition,” Higginson said in a statement. “This change in management, while unexpected, is strictly related to personal conduct matters. We are confident that F5 will be in good hands with John leading the company forward.”

Rivelo, who officially became CEO in July after training with McAdam since April, outlined plans to increase online security and software sales for the Seattle company, which helps businesses manage network traffic, as well as providing online-security services.

The company showed strong financial returns during Rivelo’s two quarters as CEO. F5 reported record high revenue of $1.92 billion for the fiscal year ended Sept. 30, an 11 percent increase from the previous year.

The company reported revenue of $501.3 million for the fourth quarter, an 8 percent increase that nevertheless fell short of analyst expectations.

McAdam said in a statement he will stick to the plans Rivelo announced during the last earnings call.

F5 has been on a rapid hiring spree in recent months, increasing its employee base to 4,200 employees by the end of the fourth quarter, adding more than 130 in that quarter alone. Rivelo had said F5 wanted to hire at least 100 people in the first quarter, which ends Dec. 31.

F5 last week was named as one of the best places in a survey conducted by Glassdoor, an online forum for employees to review employers.