This was the system at DUB last year, until circa April 2005. Then DUB airport failed a security audit, and all hell broke lose in May 2005. 3 hour lines to get through security, and (perhaps affecting you) closing of the transit facility. For a while transit passengers had to reclear security, and they had no provision for this so had to go landside, meaning clearing customs into Ireland. I don't know the current state; I changed all my routings to avoid going via DUB. Presumably by now (3 months later) things have settled down and transit is re-opened (it may only have been closed for US-bound pax). So if you want to know precisely, you need someone who has done this within the past month, as it has changed several times this year. It was an abysmal situation for a while (note that DUB is not a good airport at the best of times, poor facilities, the road into town is under construction making for long delays getting to/from the airport, and EI often has several hour long delays at check-in, along with the long security lines.