Homes in Cork, Cavan and Galway will be connected to the National Broadband Plan network by the end of the year.
Work on the new fibre network is to start in Cork and Cavan by the end of the month, with townlands in Galway to follow shortly.
National Broadband Ireland has also confirmed that minimum download speed for the network has increased to 500 megabits per second, from 150.
The group's chief executive, Peter Hendrick, says the first homes will be able to avail of those speeds by the end of 2020.
"Before the end of the year, we'll start to see homes being connected with high-speed broadband and people being able to utilise that speed of 500 megabits per second," he said.