Riverbed Technology (NASDAQ:RVBD.DL) results for the first quarter have been released. For the quarter, revenue totaled $246 million, up from the $182 million in the same period the previous year. This was thanks in no small part to the $52 million contributed by Opnet Technologies, the network-management firm Riverbed acquired last year.

Bottom line, meanwhile, dipped into the red during the quarter. Net loss was a little more than $8.1 million ($0.05 per diluted share), compared to a profit of $6.9 million ($0.04) in Q1 2012.

Riverbed also revised downwards its forward guidance for its current quarter. The firm now expects revenue of $255 million-$260 million, with EPS coming in at $0.21-$0.22. Those figures are lower than market estimates. On average, analysts had expected roughly $273 million and $0.25, respectively.