I don't generally use stop loss orders on IB but thought I would use one and watch it to make sure that it does what I think it should do. I understand that a stop loss with IB on a long trade is activated when the Ask hits the stop loss activation price and will fill to the limit price taking out the bid. I had a stop loss on the Q's today with an activation price at 32.16 and a limit at 32.06, I routed through Island. I was also watching the Island book separately. The Island book quotes jumped from 32.162ask to 31.155ask without showing 32.16. My stop wasn't activated (although I manually managed to get out at .16). Did my stop not activate because 32.16ask wasn't actually quoted or is there another explanation? In this case is it better to route through BEST for a stop loss to ensure that it doesn't just bypass the activation price?
Stops vary from market to market - options stops are different than listed stops are different than nasdaq stops. Don't know the details b/c the Q's trade on several different markets, but I believe the rules are listed in detail in TWS user's guide under 'Stops'
I have one case where I could document an IB stop on the NYSE should have been activated, where it wasn't. That was a few months ago. Has been good since then. I believe that IB has some logic in the stops requiring multiple bid/asks at the stop limit to avoid wild ECN quotes from triggering your stop.