Diop endured a frustrating campaign on the fringes at Craven Cottage last season, unable to displace Fulham's first-choice pairing of Calvin Bassey and Joachim Andersen, and does not appear to figure in new manager Alvaro Arbeloa's plans.
The 29-year-old impressed for Morocco at the World Cup this summer, a display that appears to have accelerated interest in a fresh start away from west London after four years with the Whites.
Nothing has been finalised yet, but the move is understood to be progressing well. Diop joined Fulham from West Ham in 2022 and has made 96 appearances in all competitions for the club.
Arbeloa replaced Marco Silva as Fulham manager earlier this month, signing a three-year contract in his first permanent senior managerial role after serving as Real Madrid's interim boss until the end of last season, having previously worked with the club's academy sides.
He welcomed back the first batch of players for pre-season last week, though Diop was absent from Motspur Park as he takes a break following his World Cup exploits.
Fulham's transfer business has been slow to get going this summer, though the club did confirm last month that they had exercised their option to sign 18-year-old forward Jonah Kusi-Asare from Bayern Munich after a season out on loan.
For Ipswich Town, a move for Diop would add both size and Premier League experience to Gary O'Neil's backline as the club prepares for a return to the top flight.
His performances for Morocco during the tournament in North America underlined his ability to perform under pressure at the highest level, even after a season of limited club football, and O'Neil is understood to see him as a squad option capable of contributing from the outset rather than needing time to adjust.
Fulham, meanwhile, are likely to explore the market for defensive reinforcements of their own once Diop's departure is confirmed, having already reshaped much of their attacking options under Arbeloa's predecessor.