Nov. 9 (Bloomberg) -- Cisco Systems Inc., the largest manufacturer of networking equipment, and software-maker CA Inc. led at least $10.6 billion in U.S. corporate bond offerings, the busiest day in more than three weeks.

Cisco, based in San Jose, California, sold $5 billion of notes in its third debt offering since going public in 1990, according to data compiled by Bloomberg. CA, the second-largest maker of software for mainframe computers, sold $750 million of 10-year bonds.

Borrowing surged as U.S. stocks extended a global rally. Investors, buoyed by third-quarter earnings exceeding analyst forecasts, are snapping up corporate debt, according to Guy Lebas, chief fixed-income strategist and economist at Janney Montgomery Scott LLC in Philadelphia.

“Corporations seem to be hurdling over their earnings expectations,” Lebas said in a telephone interview. Analysts have raised earnings estimates this year as “the ridiculously low expectations are slowly being withdrawn.”

Borrowers sold $11.5 billion of U.S. corporate bonds on Oct. 14.

The Standard & Poor’s 500 index posted its steepest gain since Oct. 29 adding 2.22 percent to 1,093.08. In the third quarter, 355 of 426 S&P 500 index companies that reported earnings have beaten consensus expectations for profit per share, Bloomberg data show.

Cisco’s issue consists of $500 million of 5-year notes, $2.5 billion of 10-year securities and $2 billion of 30-year bonds, Bloomberg data show.

The company has bought about 130 businesses in its 25-year history, using them to enter new markets, such as cable set-top boxes and home wireless routers.

Islandia, New York-based CA’s bonds priced to yield 5.5 percent, or 200 basis points more than similar-maturity Treasuries, Bloomberg data show. A basis point is 0.01 percentage point.

To contact the reporters on this story: John Detrixhe in New York at jdetrixhe1@bloomberg.net; Nikolaj Gammeltoft in New York at ngammeltoft@bloomberg.net

Last Updated: November 9, 2009 17:45 EST