McDonnell arrived in the 2020/21 season from fellow National League side Notts County, becoming the Spitfires’ number one goalkeeper.
Eastleigh kept a club record and joint-league winner of 18 clean sheets in the 2022/23, earning him the Player of the Season award.
The 29-year-old also holds Football League experience with AFC Wimbledon, where he played for five and a half years before his move to the Magpies.