igano, As to what caused it could be a number of things. the command "show switch stack-port diag" is often my first goto and see if there are any errors counters.if there are then it can be cable or stack-port itself. There is also a chance that the "keep alive" from that switch was just not heard from the master switch so the member switch stepped forward in order to take over the role of master which kicked it out the stack. This can be caused by large CPU directed traffic hitting the "brain"CPU of the Master switch or just over saturation on the stack-port going to that member switch.Sadly the list can gon on and on. If it continues to cause an issue I'd say update the code as they do make corrections that affect stacking.   I hope that helped
Hello I'm looking for some advice please. I have a stack of 4x DELL switches - N1548 series. They are running firmware version 6.7.1.9 Last week, Unit 2 went into a strange mode where a "show interface status" will display N/A on every column (Speed, Neg, etc) except the Link State column where it showed "Detach". Not all hosts plugged into Unit 2 were affected, only a couple of them dropped off the network. Rebooting the switch fixed the problem, however today the same thing happened with Unit3. Again rebooting Unit 3 sort it out.  Does anyone know what may be causing this strange behaviour? Are the switches slowly 'dying'? Many thanks
stack switch N1548