Tickets for the fifth round clash at the Lane only went on sale last weekend after we beat West Brom in a fourth round replay.
After Season Ticket Holders and Members bought their tickets, the game went on general sale on Wednesday - when the 12,000 were snapped up.
"It just underlines again the fantastic support this club has," said Ticket Office Manager Karen Murphy.
"The response to the tie going on general sale was amazing. The telephones were red hot from 10 o'clock through to six o'clock and we sold all 12,000 remaining tickets on Wednesday.
"I would like to thank all the fans not just for that support but also for their patience.
"It just shows how important the ticketing priority has become for our Club Members."
Our Ticket Office would like to thank our fans for their support and patience after we shifted an amazing 12,000 tickets for Sunday's FA Cup tie against Forest on Wednesday.