Cisco could be forced to pay more than $3bn to secure the Norwegian video conferencing specialist Tandberg after a major shareholder group blocked the offer.
An cash offer was tables a couple of weeks ago which received the backing of Tandberg's board it has emerged that a shareholder group with a 24% stake is arguing that the bid is too low.
Cisco has until 9 November to secure the backing for the deal from 90% of Tandberg's shareholders.
The hiccup in the acquisition comes just one day after Cisco announced a $2.9bn acquisition of mobile video specialist Starent.
According to analysts quizzed by Reuters options for Cisco include raising its offer or taking a lower stake.