Cisco ( CSCO) beat Wall Street's second-quarter earnings and revenue estimates on Wednesday, allaying concern about tepid enterprise spending. The networking company reported revenue of $12.1 billion, up from $11.5 billion a year earlier and just above analysts' estimates of $12.06 billion. Excluding items, Cisco earned 51 cents a share compared with 47 cents a year earlier. Analysts surveyed by Thomson Reuters were looking for 48 cents. Cisco's non-GAAP earnings included a tax benefit of approximately 1 cent a share thanks to the reinstatement of the U.S. federal R&D tax credit last month. The San Jose, Calif.-based firm also offered healthy guidance, predicting revenue between $12.06 billion and $12.3 billion and earnings, excluding items, between 48 cents a share and 50 cents a share. Analysts surveyed by Thomson Reuters were looking for sales of $12.22 billion and earnings of 49 cents a share Cisco CEO John Chambers struck a positive note during the conference call to discuss the results. "We continue to be pleased with the traction of our company," he said, and cited "a tone of cautious optimism" among Cisco's customers. Chambers noted particular strength in U.S. commercial orders, which he said could be an early indication of GDP growth. "U.S. enterprise and commercial, I really believe that that is the key to what the U.S. is going to do over time," he said. "At the moment, that looks good -- our pipeline is good." The CEO, however, acknowledged that other parts of the world are still challenging. "We continue to see a soft global recovery," he said, pointing to weakness in parts of Europe, particularly southern Europe. Cisco shares ended the week's trading down 0.8% at $20.99. Star hedge fund manager Leon Cooperman has initiated a new three-million share stake in Facebook ( FB), according to a 13F filing this week. As of Dec. 31, 2012, Cooperman's Omega Advisors owned 3.1 million shares of the social networking phenomenon. Cooperman, who liquidated his Apple stake, did not have a position in Facebook prior to this filing. Elsewhere, Warren Buffett's Berkshire Hathaway ( BRK.A) initiated a stake in Internet-infrastructure specialist VeriSign ( VRSN). The billionaire's holding company opened a position in Verisign, which provides domain name registry services, with 3,685,700 shares. The Oracle of Omaha also made a modest increase to his IBM ( IBM) holding, adding 597,588 shares, bringing Berkshire's total to 68,115,484. Facebook shares ended the week down 0.79% at $28.32, while VeriSign was up 1.65% at $46.14. IBM's stock was down 0.35% at $200.98.