Cisco Systems ( CSCO) previewed its second-quarter earnings, saying they will exceed the consensus earnings and revenue estimates, after an executive mistakenly sent a memo to employees characterizing the results "in positive terms."

Cisco, which had been scheduled to release the results after the closing bell Wednesday, was expected to earn 5 cents a share on revenues of $4.5 billion in the quarter, according to First Call.

According to a press release, the memo said the company's booked orders for products only were $3.9 billion versus an internal goal of $3.75 billion for the quarter. The memo didn't include specific information about revenues or earnings for the quarter, but Cisco said it was releasing the outlook Wednesday morning "so as to minimize any potential confusion."

"We felt it was necessary to disclose this information publicly, given the broad internal distribution of the communication," Cisco said. The company will make its normal earnings release and hold its conference call after the market closes Wednesday.

Cisco was the most actively traded stock in the Instinet premarket session, trading up 2.9% to $19.04.

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