Networking specialist Juniper ( JNPR) is feeling the strain of the tech spending slowdown, and expects first-quarter revenue well below its initial estimates.

The Sunnyvale, Calif.-based firm, which released its preliminary first-quarter results after the market close Tuesday, blamed lower-than-expected service provider sales for its revenue shortfall.

Revenue for the quarter is now expected to range between $760 million and $765 million, below the firm's initial guidance of $800 million to $830 million. Analysts had estimated revenue of $794.32 million.

Despite its weaker first-quarter revenue, Juniper's shares shot up in extended trading, rising $1.63, or 10.44%, to $17.25.

Juniper, which competes with Cisco ( CSCO) and Alcatel-Lucent ( ALU), has not been having the easiest time of it recently. The company's shares plunged last month after a report from Lazard Capital Markets pointed to growing order cancellations and delays for the network equipment maker.

The company, which will release its full first-quarter results after market close on April 23, is nonetheless reaping the benefits of its ongoing cost-reduction efforts. Excluding charges, the firm expects non-GAAP operating expenses between $375 million and $380 million, compared to its previous guidance of approximately $408 million.

Juniper also expects a non-GAAP operating margin of around 16%, resulting in non-GAAP earnings of 16 cents to 17 cents a share, within its previous guidance of 15 cents to 17 cents. Analysts had estimated earnings of 17 cents a share.