Just a tip to everyone with packet lost problems with a fast ethernet mikrotik product (R433,R433AH and so on) and ECI switches and fiber converter products with gigabit ports, we found that if you plug a fast ethernet (on mk) to a giga port (on ECI) even if the ECI port is set to 100mbp/s they will not talk with other properly. We tried several mk products with no sucess. The only way we found to solve this is to plug a giga port mk product and use it to bridge the other fast ethernet mk product.
I know the next question would be why do i want to plug a 100 mbp/s to a giga port anyway? This specific operator only deliveries on giga port even if you buy 2 or 4 mbp/s of internet and to keep our costs down we we were using the RB433 plugged direct to the ECI port with no good results.
Can you give some link to ECI product line and specify models what you use?