Juniper CEO Kevin Johnson's conference call comments have been added to this story.

SUNNYVALE, Calif. (

TheStreet

) -- Weighed down by an uncertain economy,

Juniper

(JNPR) - Get Report

missed Wall Street's estimates in its

second-quarter results

Tuesday and offered tepid third-quarter guidance.

The

Cisco

(CSCO) - Get Report

rival brought in revenue of $1.12 billion, up from $978 million in the prior year's quarter, but below analysts' estimate of $1.15 billion. Excluding items, Juniper earned 31 cents a share, up slightly from 30 cents in the year-ago quarter, but below the 33 cents predicted by analysts.

"Juniper's results reflect momentum in our routing business and a return to solid performance in switching," said CEO Kevin Johnson in a prepared statement. "A number of factors, however, including mixed signals in the macro economy, impacted our performance this quarter."

The company expects third-quarter revenue between $1.07 billion and $1.12 billion, compared to analysts' forecast of $1.22 billion. Excluding items, Juniper is looking for earnings between 26 cents a share and 30 cents a share, well below Wall Street's forecast of 38 cents a share.

Hints that Juniper is experiencing

a tough demand environment

have recently surfaced, most notably Johnson's

cautious comments about government spending

and the impact of the Japanese earthquake on the company's supply chain.

"There are questions about how quickly

Japan will shift to capital investments on new projects," added Johnson, during Juniper's second-quarter conference call, also noting weakness in the telecom sector. "Service provider capex guidance for the second half has been lower than seasonal guidance."

Juniper's cost of sales as a percentage of its overall sales, however, has fallen dramatically year over year, from 63.29% to 35.36% in the second quarter. This shows that the company is spending less money to generate each dollar of revenue.

Johnson also noted that Juniper's switching and routers sales are robust, with revenue growing 33% and 21%, respectively, year-over-year.

The CEO said that, while he is cautious about the second half of this year, he is very optimistic about 2012 and beyond. The continued growth of smartphones and tablets is creating demand for network innovation, he added, during the conference call.

Juniper's results nonetheless spooked investors, who pushed the firm's shares down $5.00, or 16.04%, to $26.17 in extended trading.

--Written by James Rogers in New York.

>To follow the writer on Twitter, go to

http://twitter.com/jamesjrogers

.

>To submit a news tip, send an email to:

tips@thestreet.com

.