Unfortunately the switch is only able to mirror individual ports as source ports. You can confirm this by testing setting up a mirror session where the source port is not part of a LAG.
Hello, Is it possible to port mirror using as a source, a LAG, consisting of 4 ports (2 in each member of a stacked set of PowerConnect 6248s). Everytime I try adding the source, using GUI, I get an error:  Error! Failed to Set 'Type' with 'Tx and Rx' error occured FILTER_MISSING What filter is this referring to? I cannot select as a source, the unit 1 or unit 2, members of the LAG, as the gui does not show them in the drop down list of ports. Thank you.
Port Mirroring a LAG on stacked Dell PowerConnect 6248s